depending on bonus research, a single drone will transport 1-6 stacks. having that capped for requesters to 1/3/5 stacks would make no sense and slow down transports a lot. and with steel chests having 48 stacks, the small 1x1 providers could hold enough stacks for 8-48 drones, up to 72-288 drones on the 3x3 and enough items for 200-1200 drones on the 5x5 !!!
thus YES, some smaller footprint might be useful, eg when i want to provide 4 different items to a single (or at most a few) assemblers. but also NO, the above values are too small and too large and would need a lot more balancing, and there already are limits to the capacity of depots anyway (roughly 2 steelchests capacity on providers, which would take a lot of inserters/loaders to fill them fast enough; and depending on bonus 100 to 600 stacks or maybe a few more for requester depots when you have up to 100 or maybe a few more drones in the depot)
hehe, a 1x6 or 2x6 sized provider depot might be nice, to be used at train stations :-) currently i am using two 3x3 providers to unload a single wagon into, but that quickly becomes unbalanced when drones always take from the nearest provider which most often gets empty quickly, while the second is full and unloading time increases/doubles. I'll have to experiment how buffers as relay between train station and the rest of the factory may help.
another problem that i have with number of stacks and stack sizes is that i want/need many large transports for ore (even with max bonus, this is only 6x50 = 300 ore each time, and i need many drones to get enough ore, but on the other hand, researching this big bonus also causes drones to fill requesters for green and red circuits or for science potions with insane amounts of items (a single! drone causes a requester to try and stay between 6x200=1200 and 12x200=2400 items) ... would it be possible to add an option to the depots' popup window that reduces the bonus, similar to the "override stack size" on inserters, to let drones from a specific requester only carry and ask for 1 to <current bonus> stacks per drone ?