Anyone played a single sector challenge yet?

I did a game on tiny where I didn't colonize any other planet. But I did conquer rather than win science-wise or alliance.
I think this could be made for an alliance victory quite easily:
Ally yourself to the altarians or Torians (Altarians more trustworthy), then help them (culturally or by selling ships - culture is probably better as you'd hand them the planets you turn. You can probably get even more allies that way).
A science victory would be more challenging.
Which one do you target? I guess the strategy will vary depending on the goal.

I've played a 'one planet galciv' a couple of times, it's a fun way to spend some time and very different from most games. You can get some really interesting diplomacy, I've had races offer me dreadnaught tech for free, for instance. I didn't try for a win with either of mine, I just wanted to see how long I could last as a semi-isolationist (freighters, tech trading/selling, but no alliances, no military besides defense, no starbases except in home sectory). It's surprising how long you can hold out this way.

Play with a tiny 4x4 map and rare inhabitable planets. The only class 15+ worlds will probably be the home planets for each major civ and each minor civ. It is amusing to use your initial colony ship to scout for resources, and then put it on your homeworld for the extra 100 population.
It's important to keep the balance of power. You can't allow another civ to get a 2nd planet, or they'll become too powerful. I also find myself donating culture-upgraded starbases to minor civs, to keep them in the game, especially if they're my trading partner.

The only thing that ruins the one-planet game is if you get a random event that forces you to invade another civ (Draginol or artifact). In this case, you have to invade and then sell/give the planet to a minor civ. You also can be ruined by the random event that turns Earth into a class 10 planet. In that case, you're allowed to move to another planet.

I have just won a game by just staying in my home sector in abundant/scattered/medium/bright galaxy. I had a class 26 planet in my starting sector, lucky me and a class 16 planet to boot for total of three planets. So I just settled the two and grabbed a research resource and went straight for the early game wonders and trade goods. I got all and managed to stay ahead, technology-wise and built up three maxed out production starbases in my starting sector eventually. I had to pay tributes sometimes but managed to avoid war all game long. The Altarians were threating to dominate the galaxy and they were allied with the Torians. I had to work hard to keep them from dominating by supplying a LOT of dreadnoughts and later, avatars to the Dregs who were constant at war with them. Most of the game I had two of my planets chugging out dreadnaughts every three turns or so to give to the Dregs while I had the third planet chugging out constructors to build up production bonuses. Despite my efforts to keep the Altarians contained, they eventually crushed the Dregs and ruled a majority of the galaxy. Fortunately I was close to technology victory by then. I never went out of my home sector but I had an annoying problem with a nearby Arcean planet that kept defecting to me all game. I didn't want the planet at all because it was backward and I would have to build it up and that mean raising the social production slider from zero ( my three planets were all built up already) and that would be a big waste. First time, I gave it back to the Arceans but the planet defected back to me again in couple of turns. So I gave to the Dregs, but the stupid planet came back. Gave back to the Arceans many times, then eventually I tried abandoning it a few times but the Arceans kept settling it and it kept defecting to me again in a few turns! I guess I should not have built all that influence-enhancing wonders and trade goods! It was definitely an interesting game.

~SDC~

I played by Jeff's proposed 'rules' yesterday and won. I had no resource, and limited myself to one starbase in addition.
I thought I had asked for rare planets on a tiny map but there were many. The biggest civ in the beginning were the Carinoids with 3 yellow stars.
I managed an alliance victory (how to get the Drengin to love you: Flip a Torian planet, give it to Dreng. It flips back, give it again, repeat and rinse).
My strategy wouldn't have worked against incredible ai's.

I love to play masochistic tiny maps, which usually turn into one-sector games. I almost always get munched, too.

One starbase? Well done. I had four - mainly for trade boosting. Don't think my economy would have survived on one starbase (but don't really know how much of a boost they were giving me).
Won on small/occasional/bright (with Arcs on Intelligent) via tech victory.
One thing that suprised me is how far my culture was extending across the map towards the end. I was under the impression that starbase/Civ culture would only extend out one sector - but it covered a fair bit of the map. I also had the same thing with the Carinoids. Three yellow stars. They were the most powerful Civ through most of the game. Even when I won.
The other civs were attacking each other but noone messed with them.
I was close with the 3 remaining Civs at the end but couldn't ally as they were each at war with at least one other Civ. Wouldn't mind a SMAC-type 'Please make peace with so-and-so' dimplomatic option.

Now trying medium/abundant/scattered/bright. (Not game to have any civs on intelligent. I am already getting messages that they are builing manufacturing and economic capitols before I have even built Manufacturing Centers... so don't know how I will go here.

I have also used someone else's tip about how the AIs use attack numbers when gauging how powerful you are - so if I am at battleaxe/defender stage I have a few starfighters in orbit to keep them away. So they didn't declare or threaten war on me once. If they had I would have been toast. Bit cheesy but seeing as I am limiting myself to one sector I don't feel guilty.

I will try a one planet game a bit further down the track like the other guys have said - but at the moment I am not adept enough with the economy side of things.

My strategy was to get Trade Goods and sell them for a profit (techs and cash). This makes economy largely irrelevant. Then add som etrade ships and keep a trade good for emergencies.
It doesn't work with the toughest AI's because they won't give you cash no matter what (except the Alexians).
Part of the strategy was to play the ai's against one another. For example, the Drengins asked me a few hundreds or thoudand bc. I paid, then gave whatever ws needed to ALL other civs so they would wage war against the Drengins. I also relocated my trade routes with them to the friendlier Torians, so their income suffered a lot. They were also too busy with the other ai's to keep pestering me.
I agree that culture extends very far. My starbase was culture maxed (so I'd flip planets to sell them back), and I almost won culturally (with just 1 starbase).

About diplomacy, you can ask other races to make peace. I don't know SMAC, though, so can't compare the UI, but I did use it later in the game to convince the Torians to stop pounding the Drengins so I would win allied with both (Torians should have finished the Drengins much before, but they didn't send ready transports on unportected planets within 1-month range...).