I'm pretty sure the unfinished bits of the BoXer were the AGA. I imagine it has taken several years to do the AGA for FPGAArcade.
Short answer: No
Buy an A600 and an FPGAArcade later. Like others have said there is very little AGA software worth having.
The best points of an A1200 would be installing a faster CPU. Or not having to hunt down the rare 030 upgrade for the A600.
The A1200 might have more upgrades, but they are not easy to get.