I disagree with research trees semi-randomly developing. If anything, make this an option. Here's why: I like to play Rebellion against 9 computers set to Vicious. It's only possible if you know which technologies will be available. For Tech its important to get a great economy including Trade and Pervasive Economy early. For Vasari, starbases and their upgrades are critical. For Advent, there's a couple ways to go, but culture spamming is the easiest. If I had to muddle my way into finding critical subjects, I'd be slaughtered.
I think allowing repeat research is the way to avoid a " cookie-cutter research path".
One of my favorite custom mods for Rebellion sets the maximum level for most research subjects to 100. It really allows for specialization. If you want 100 levels of shields, they get expensive, but they are nice. One siege frigate powerful enough to blow up a planet is possible, unless the opponent has researched enough ground defenses to render them useless. I've seen light frigates more powerful than capital ships. And I like that level of specialization. The AI doesn't know how to cope with the changes, so they can be beaten on any level (with the exception of an occasional Advent stalemate condition). But it's hilarious falling back to an overwhelming fleet of carriers, until they jump in to a system maxed out with starbases to the point no more will fit in the gravity well. Then hearing a friend shouting and cussing across the room. Having enough research depth that even though everything is unlocked, research can still progress is a great way to add variability to the game.
I'm not a fan of the tier system. It just doesn't logically make sense to me, to be at point where research stops until you research how to research. It would make more sense if the tiers unlocked as soon as you researched half the prior tier and had the proper amount of research labs (I guess if you absolutely hated the prior tier you could research general studies to bypass it.)
I also prefer setting the research labs to only required one Civilian slot instead of 4. This allows players to choose to specialize instead of expand earlier, especially in a small map or asteroid heavy environment.
I realize the game is in the brainstorming and experimental phase, so I apologize for sounding like I'm shooting down ideas before they get explored. Ideally, when a new idea comes out, I'd like a check box to enable or disable it and see which version I enjoy better. Absent of the ability to test both ways, I feel I have to play them out in my mind and anticipate what I would like better. In this case, I know that if the map and players dictate I choose one type of strategy over another, I don't want to be hamstrung by not being able to research it.