LoadBalance, proxy, LoadManagement

As my whole wireless network (9APs, 100 cpe’s) is on MT, I’m in the process of replacing all my proxy servers & routers to Mikrotik, there’s a few questions:
HARDWARE:
I was thinking of a RB532 (which I have) with daughterboard for more LAN ports & big as possible flash expantion. (How big?)
OR
I could get something else?

ROS SETUP
a)Load balancing: No of WANs; can I load balance through more than 2 WANs evenly?
b)Load balancing: Https; Is the sample in WIKI that claims to load balance and keep 443 sessions intact working ok for all websites?
c)Load balancing: Management;
I’ll have 4 outgoing lines:
No1. dedicated to users connected via PPP, unshaped. All P2P traffic(but not Skype) must go through this line.
No2. (cheaper no international line)load balance with 3&4 but prefer all local country trafic (IP ranges) through this one
No3. load balance with 2&4 but force all SSL international traffic through this one
No4. load balance with 2&3

Possible?
d)Load balancing management:
Can you distribute next gateway according to how many sessions in use or how much bandwidth used per WAN, in stead of just round-robin?
e)caching/proxy: Is ROS3.2 web-proxy able to cache all, like windows updates succesfully? Performance?
f)caching/proxy: Can you exclude certain ‘url contains…’ websites from caching?

I’ve read many examples in the WIKI, but would like to get honest opinion before I make the plunge.