How about making a new special unitstate "auto-share", and a player whitelist to whom you may automaticly lend units should they request (select a unit and press hotkey/button, should you decide to take unit back you just repeat the process, since you were original owner you can do it regardless if player removes you from whitelist)?
Because if you play as a bro-clan, you may have only single player to check whether all mexes are working intact, grid is connected and so on, he may request (take) any con and get it to rebuild destroyed stuff, without spamming next key sequence:
[alt][enter] GIVE ME A CON PLS FAST
While all the other eyes will be constantly glued to battlefield.
Also in similar way we could have shared striderhubs (oh god why every player has to build one for himself!?) and maybe even factories in special cases.
How is it different from current share? Well, currently YOU give units, while this way you may allow ally or clan member to TAKE units (specific units or specific unit type).
I know we have /take command, but that doesn't work until team resigns.
Also this would help to play coop with AI, since you may not take entire AI base, but some of it's units, and then give them back... Or not.
edit: Just in case anyone wondering about selfd allies, you won't be able to, you damn traitor.