Have you or do you use a restream service?
I use restream.io and Mobcrush for Vimm because restream.io is not free to stream Vimm.

Do you pay for a restream service?
When the service is on sale and budget-friendly for a year.

What features are a must-have (i.e. chat combining, announcement bots, platforms, etc)?
Chat combing, integration is a must because I stream on Twitch, Mixer,Vimm, and sometimes Periscope

Would you like to pay in HIVE for this service?
Yes, I would pay.