I don't really mind playing the html version, so unless you are interested in adding a number of more technically ambitious features (e.g custom window size/placement for the porn GIFs, easier modding tools, etc), I don't know if porting it to a new engine on its own would add much to it.I'm seriously considering doing some new work on TF Card Battle. I've got a couple options and I'd like to know what people would be interested in.
A: Just more content added to the HTML version. The easiest thing but the least interesting to me personally.
B: Porting the game over to the The Monster Within engine. Wouldn't be that much work, although has issues with art. I don't know if people really want that over just playing the HTML version though.
C: Make a full-fledged TF Card Battle 2. This would be very far off, I'm talking years from even starting production. But I could start exploring design space and such if people like the idea.
Now if we're talking about a full blown sequel, I don't really know how the mechanics could be expanded, but I guess I'd just say that my favourite part of this game was how the porn interacted with the "progression" in the game, both in terms of game-state of the individual matches (stronger cards involving more hardcore sexual acts as a desperation tool only usable with your "near death" mana) and of the overarching campaign (mainly the hybrid decks, was fun to see what porn footage and themes you had to find to make those work), so I would like to see more mechanics that try to expand on that design.