SL does not need more than 12 teams.
There simply aren't that many clubs that are worth the elite level funding, and the gap in quality week to week doesn't need to be stretched further.
If there's extra money to be spent, close the gap between Championship and SL.
I could accept an argument that there should always be 10 British teams in Super League as its a British comp. But it would come with the caveat that foreign teams should be ringfenced out of P&R, and have separate funding arrangements with the League that take into account their strategic value and future broadcast deals in their countries.