At low AIP, yes. At "higher" AIP, errrrr... no.
Well, in my two recent 7ish games I've been downright careless about AIP (playing much of it around 300) and it's just not hard. There was the one time I forgot an avenger, and that was... interesting. But considering I still won, despite that going heavily pear-shaped while in the neighborhood of 300 AIP, it seemed pretty tame. And I'm not actually all that good at the game.
Errr... I'm not actually that good either, since I did not even notice than penetrators ignore shields. Yet, I did win this game. I was going for a win with 10K first, but I found it unecessary to unlock stuff. What I feel, however, is that I abused the AIP mechanic.
My opinion is that even with the proposed changes, and no superweapon, it's probably doable to win with ultra-minimal unlocks. The only "real" difficulties I encountered where the drone thingies (AI brutal pick), and the Exos. I don't remember killing more than one zenith reserve, getting all of them killed and setting them as a garrison in my homeworld would allow me to defend against the Core retaliation waves, with whatever ship I get with reclamation. With the ARS not unlocking lvl 2 ships, I would still need 4 caps of ships (out of
to kill guard posts. It would be slower, but the 4 other caps (+starships) would be enough to defend against waves and stuff while the "attack fleet" cleans the first homeworld. Second homeworld could be killed with the entire fleet.
That's why I'm insisting about reinforcements and AIP on top of this.
At 50 AIP and diff 7 the AI does nothing significant enough to pose any kind of threat. IMO, that's when the game is decided. AI worlds are guarded by guard posts and have at most 100 ships (my own fleet are in the 400-500s with a few ARS). Yet, with 50 AIP, a moderately experienced player is in position to take the first homeworld without alerting it, so the main challenge is the guard posts and not the AI response to your actions.
With an AIP to 150, the AIP spawns groups of 30-60 ships per reinforcement phase. With only level one caps, I'd need most of my fleet to clean a world, and it would be more difficult to use level 3 - 4 worlds as highways. Of course, you could also raise the AI response when 50 AIP is hit, but that would again reduce the "max AIP" before a game can be won... which I feel is low enough already.
That's why I would be advocating that the "lowest AIP possible" before getting a shot to destroy a homeworld should be 150, and not 50. First of all, because it would make the answer from the AI much more significant before I'm able to be a threat to the AI.
I think I'll try this kind of game (with no superweapons) later to check if I'm right.