Your 3) and 4) are in opposition. Your 2) and 4) are in opposition. Yes I think 3A max per port but say 8-9A total as for each extra port the chance it needs maximum power becomes much less.
Portability means you must solve a portable person's problems. A portable person will have 1 tablet, 1 phone, and say 1 portable charger and say 1 BT charger, so set a power budget for that.
I don't think one 4-port with 2 lots of 30W each is viable in a compact design. I'd say set a maximum budget which really dominates size of say 40W and then say one USP-PD 30W and the 3 ports upto 3A each and they fight over the 40W, so say 30W full power leaves 10W for say a Powercore 1000 needing 10W, or a phone needing usually 7W and say a BT headphone needing 1W. That sort of thing. If you plugged in more power demanding devices then say that 30W drops to the next profile 18W.
Full power to every port is more for the desktop chargers when a family all plug in power demanding tablets at once.
Hence really two models, one 4 port 40W with one 30W USB-PD, rest 3A max, and one 4 port 40W each 3A total.