It would be amazing, I am a huge fan of your skins!
I was thinking if others joined in, we could make collaboration thread in the contest and give-aways forum maybe? I know it's not really a give-away, but it's close.
And write in the custom skins descibtions the dates they'll be cheap in.
So if we made valentine-skins, we could upload them to custom skins a week from now to have them accepted, but with a price of 50 gold. Then write in the descriptions that they're available for cheap silver from Sunday the 13'th Febuary, till Sunday the 20'th Febuary 2017? That gives a relatively large window for the first time, and if people catch on to the idea we can change the details.
We can also write together before uploading skins and make sure they match and doesn't overlap, and then make collective sets? (Like you said, sharing/collecting seasonal skins would be neat)
(Been playing with the idea for a few days ^^'')