The EX3 can shoot in HDV mode.
You certainly could make a picture profile in the EX that may match the A1
EX 1/2" CMOS at 1920x1080 vs 1/3" CCD at what I'm sure is a smaller pixel count for the A1 can be a significant factor when it comes to resolution, Depth of Field, Low Light Performance, rolling shutter on flashes or strobes.
I'd choose all EX3s unless there was a reason to go all A1 (and there certainly can be).
Why make all this extra work especially when you're basically "dumbing down" (negating its assets) a great camera to match three others?
Of course you can develop a style which assigns the EX3 a specific role so it's differences work to your advantage and that could be interesting. One example might be as a close up steadycam operator who can shoot in dark corners, do close ups throwing the background out of focus, get hit with the odd spot light and not get that "CCD streaking."