Passing on another idea from my 9yo son. I tried searching and didn’t turn up any results, so hopefully this hasn’t been already proposed.
Allow people to give drops they have earned (or equipment from their garage) to other Zwifters.
His motivation is partly (1) to help his younger brother (who has very few drops and can’t afford “anything cool”) and (2) to use as betting-type prizes for races between Zwifters, etc. 
Great idea, love the second option! 
Wouldn’t this encourage (a) farming, and (b) real-world cash transactions for Drops/equipment?
Yeah, I think that’s a very good point. And probably a logical conclusion. Maybe it could be limited to discourage that. I’ll use that as an economics lesson for my son.
If transactions were limted to drops only (no in game product) with a maximum transaction size it could discourage farming. I would happily give away drops as I accrue them quite quickly and simply don’t want anything from the drop shop. I have purchased some bikes and wheels in the past just to burn drops.
I’m sure Zwift have resisted introducing in game trading to avoid farming and external ‘cash for product transactions’, but surely there has to be a way to allow people to share when they have an excess of drops.
Perhaps one could only give drops to followers, with a limit based on how long they’ve been following you. Say, 100,000 drops for every month of following.