Generally I think a turtle style feels way more comfortable for new players, and this is reinforced by a bias towards safer maps like gap or astro when it comes to the games they play.
For them to become ladder players, if they ever do, they have to go through a phase where they unlearn some bad turtle habits, and try out and succeed at being aggressive. They tend to do this by playing more open maps in custom lobbies, the lower the skill and confidence, the more players.
There's already a big cost in attention needed to use the ACU offensively, as compared to just making some obscene firebase with a t2 com, a very, very common noob trap. And attention, specifically, is a beginner's most scarce resource. They often forget radar, tmd, scouting in general, they may idle their first high tech engies for minutes if they get distracted, or attack then look away from the fight, because doing these things right is not yet second nature to them. They spend more time doing any one thing and often get tunnel-vision on some random task because they have to think about it and it's not just busywork as it is to a veteran. This makes multi-taksing harder.
I'm worried about the nerfs you suggested because they make the climb from astro noob to ladder player steeper. I'm sure, FTX, you're very familiar with all the things I described, with all your mentoring experience on discord, and with that in mind, maybe I shouldn't be worried, but I'm still hoping you can think of another way of solving the problem.
I think the recent speed boost to t2 is a welcome change, and in general, I think I'd prefer some solution (which i don't claim to have) that emphasizes decision-making. The same way an air player rushing t3 air might conclude he has a window of opportunity and a need to do damage with a very early strat if he sees his counterpart making t2 bombers, and the same way a less skilled air player like myself decides to pay a mass tax and always shield their t2 pgens, even as i know some better players skip this sometimes, by scouting better and being able to determine if they're far enough behind that a shield is needed.