Thank you for your thoughts. I really like hte option I pur forth above with "sealed boosters" for Season / Competitive / Ranked" play - in addition to the "all out" play using your own cards.
The cooldown could be reduced to each conflict, or perhaps it has "summoning sickness", or is reduced to a lower level.
I'm not sure what that solution is, but as I've stated multiple times on discord, a star basketball / baseball / soccer / formula 1 whatever athlete we're talking about can't play for multiple teams in the one season.
There's got to be some compromise.