I like where A3 has gone compared to the A1 I played a while back. I would encourage you to test A3 a few more times before changing it as it felt pretty fun and well developed to me today.
The one thing I want to suggest is adding a forward spawn for each team that moves on each cap, or at least for the Blue team. The reason being that 3CP is much closer in size and pacing to about half of a 5cp push map, and those forward spawns really help even things out and prevent situations like Red pushing back into an area or alleviating problems that arise from Blue having no engineers (or just one engineer who is being harassed). I think this is actually really important - I spent years trying to figure out 3cp attack/defense, and I think that's the problem with most 3cp a/d maps.
The connectors between A and B are also very narrow and grindy, and seem to have larger entryways and more visibility on the Red side, meaning a push from A to B is really hard if Red takes control. They get to watch narrow entrances from a wider range of areas. A forward spawn near A would help with this (I would suggest along the side with the water) but probably more should be done there.
Finally, I don't really like how hard it is to see where Blue players are when exiting the spawn at C. I think just a fence, or maybe partial obscuring, would be better. It sucks to have only 2 directions I can leave from which are basically the same, and be totally unaware of which side(s) Blue will be shooting me from. It feels like once they're on C there's nothing you can do. That's somewhat true of B, as well, but it bothers me a lot more on C because B is already so defendable.
I hope I get to see where this map goes as it seems very strong already!
