I suggested it so I should probably actually do it. Here is my list of languages that might be includable in the polyglot. I only gave these a very cursory look so some of them might actually be impossible or very hard.

??? http://esolangs.org/wiki/%3F%3F%3F
ETA https://esolangs.org/wiki/ETA
gs2 https://github.com/nooodl/gs2
Vitsy https://github.com/VTCAKAVSMoACE/Vitsy
Beam https://esolangs.org/wiki/Beam
Straw https://github.com/tuxcrafting/straw
STXTRM http://esolangs.org/wiki/STXTRM
Starry http://esolangs.org/wiki/Starry