I made my own Fc for this specific reason lol I can use the company chest to send stuff between my char and alt freely. I am pretty sure they did not implement it cause there must be a gil selling/bot issue somewhere in there but as stated above it can be bypassed I see FC group of bots farming stuff all day like shards/snurble tufts. I solved my space issue though by paying extra per month for 2 more retainers those are filling up also but it has helped a lot. I would love more armoury slots though for those gears I just like to wear for fun sometimes or since I am lvling multiple chars I have all different pieces of gear different lvls and it fills up pretty quick I had to dedicate 1 retainer to hold all my armor until I lvl those classes again.