If expansion happens the Schooners group would be paying the league to join. SSE would be investing in the league not the other way around. No need to have an either/or discussion.
Also, since the league nor any of the teams actually own the stadiums they play in, it’s not theirs to put a dome on.
Fargodome cost about 50 million USD to build/90 million USD in today’s dollars. About 120 million CAD. To build 8 of them (BC being already in a dome) or 9 if you include Atlantic is over a billion dollar ‘investment’. Half of the season is in the fall anyways unless there is a breakdown of ratings in the regular season that suggest there is a significant difference in ratings to maybe justify and an increase that will cover that expenditure, seems like a bad investment to me.