Heres one fun tactic against a sova rusher (For someone to really rush you with sova and not meet your lrm/assailants/mass-units, you have to be like within 3-4 jumps max of each other's HW right?)...
When you start, if their that close to you (and your scouts see a sova)...Make like 3 light frigs along with the colony ship..Send those to clear out the asteroid near you. Send YOUR cap ship (Marza works great here for example) to their asteroid. Pump your cash into upgrading the asteroids with extractors/etc. Once your cap kills his asteroid, colonize it and get extractors there too.
If his sova is in your homeworld? IGNORE IT! If its level 1-2, its a 30% drain and the asteroid economy very much offsets any of that loss...If you have HIS roid too, you have better economy (just use the black market effectively)... If his sova is level 3, he bought levels and wasted a ton of cash on that too. It will be a long time before the 30% to 70% sova ability "jump" pays for that level-buying.
While his sova is probably demolishing your factory at your HW, your cap is done with his roid and going to HIS homeworld to kill his factory/labs. By then your 3 light frigs can go support your cap too. So now you go and upgrade one roid, making a frigate factory and maybe military labs to get LRM if your tec...whatever works depending on race. Make units at the roid, get enough forces together, go kick sova out of your homeworld.
I've beaten a number of sova rushers this way before, not that hard. Sure, having the RIGHT capital ship helps alot here... Marza is good at taking their roid fast, vasari evacuator is great at killing his stuff with DOT's and can colonize fast (plus no colony frig woot!)...If your advent, going with HuntingX's method stops their embargo cold with proper micro too (radiance).
This is a method to stop VERY fast sova rushing. Before they have LRF class ships, etc. If they wait till they have LRM/etc before going in with sova, you should have enough units to scare off the cap ship by then too... Or you should be the one being aggressive and attack him first...Kinda hard to use embargo on defense

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Hope this helped a bit.
-Drexion