Do you plan to use both tftv twitch acct's to stream 2 matches at once? I haven't kept up enough to notice if it has happened, and if it can't, is it beause a shortage of matches (that are good) or of production team members?
Are you also interested in using the second stream to let people cast lower divs (Advanced in particular), or at least cast those games if Invite is not playing that day? I'm not sure how it would fare with views but some games last season were really close in that div, and to see if offically casted could be quite cool.
I found the TFTV casts to be enjoyable to watch, especially in the background. Game coverage was great when RGL was casting the top tier matches.
Answering the question about being open to cast other game modes, I think this should be strictly 6s. As RGL already has very strong presence in the HL community for casts (Not to mention KritzCast, if they still do it), I see it as pointless for the most part.
Looking forward to another season with even better casts!