I think that any channel that wants a per-subscriber fee over a certain wholesale price ceiling (perhaps $1/month, indexed to inflation rate) should automatically either be "opt-in" or at least "opt-out" - I would be happy to drop several expensive overrated networks in this fashion.
Combine this with a requirement that allows MVPD (cable, satellite, IPTV) providers to require a complete package subscription (no opt outs) for no more than 24 months after purchase (ideally 12 months).
And, the kicker - all networks have the choice to make themselves available free for 30 days out of each 365 day period, which all providers must pass thru to all customers as a free preview that cannot be charged for, as long as the customer subscribes to *something*.
The only exception would be if a channel airs content rated higher than TV-G for more than 5% of its broadcast day, averaged over the past year, then providers would not be obligated to offer free previews of it to those who have bought a "family package". Also, any subscriber would be able to opt out of free previews if they really did not want them.
This would allow niche services a fair chance to be seen, without forcing anyone to pay for them.