It's all about choices. Any number that's a square (4, 9, 16, 25, etc) can be wired to the original driver's impedance. So yes, 16 can be wired into one 4 ohm load.
If it's nearfield it's all going to be one channel, so that's fine. If you're positioning around the room you'll lose the ability to individually eq/time align each "bank" of however many JBL's you have. Does that really matter? Depends on your goals and equipment. Likely will be more than sufficient for one position.
I'm probably going to do an amp per 9 for at least front L&R, and call them Sub1, Sub2. I'll do an xls2502 into those, which is a little over 250 watts to each one. The next 9 may be center, may be scattered around. I'll at least have 6 of them per amp (sub3, etc.) If I do 6, I'll probably just drive a bridged xls1502 into them at 6 ohms (3 internally in series for 12 ohms, paralled with 3 more of the same = 6 ohms), an xls 1502 will do about 1050 into 8 ohms, 1550 into 4 ohms, so call it about 200 watts per driver, and the higher impedance is easier on everything.
When all is said and done, I'd like 3-5 discreet equalizable and time alignable "assemblies" that I can glom together and eq for the major flavor of bass. The nearfield will be equ'd seperately and global eq will NOT apply to it. I'll probably keep the dozen I have on existing duty, but I would like to make nicer cabinets. I wonder what I could sell carpeted triple 12 enclosures for on Offerup/CL.