Have you or do you use a restream service?
I don't, but if I did I'd use a local configured nginx server that streams to multiple endpoints (restream.io and to the platforms that are not included in the free package)
Do you pay for a restream service?
no
What features are a must have (i.e. chat combining, announcement bots, platforms, etc)?
Difficult to answer this as I prefer to write my own "features". But if I'd use a third party feature customization is a must
Would you like to pay in HIVE for this service?
No (see answer 2)
@vimm or 
@threespeak?
RE: Attention Streamers! Read this post