Poloniex here. Grin is already the single most difficult coin to support given
- Amount of effort it took to integrate
- Breaking changes that happen regularly
- Support tickets from users
- Difficulty keeping the wallet running
I do not want to delist, but such a change like this could require further large investment of engineering resources and I cannot guarantee that our product team will approve of the outlay, despite my personal passion for the Grin project.
I recommend keeping HTTP/HTTPS as an option permanently in order to reduce burden on exchanges.