Btt70s will absolutely feature the Mystery Card element. The thread you linked was talking about possibilities for an additional option.
Thanks, though, for bringing up the FantaSim feature. In my opinion, it's a good idea. The collusion example Jimmy C brought up does exist, but in my opinion it's minor, because 1) trades should, by definition, benefit both parties, at least ideally, and 2) you can collude in any of the non-Mystery-Card games as it is using regular trades. Such practice is ostensibly suppressed by your eagle-eyed leaguemates and our Collusion Policy, and it would apply here as well.
I'm gonna put it to a vote; stay tuned.