Since the main issue doesn't seem to be lack of interest but instead lack of capability, maybe the better solution is to go with
shoddybattle or
pokemon online. I understand that the use of sims would probably create a less casual environment than you're shooting for, but to me I feel like the casualness can still be achieved through other restrictions (here's a fun one, challenger's teams can't use any of the top 10 used OU's based on smogon's shoddy server statistics. I've heard it's a fun meta to play in whose only real fault is that it's kinda togekiss heavy), or by banning pokemon that are no fun* to play against (breloom because of spore, jirachi and togekiss because of flinching, skarm/bliss combos because of prolonging matches). Or by adding or removing certain clauses that competitive players enjoy/don't enjoy (say, playing with item clause or playing without species clause). While a lot of these can produce some unbalanced gameplay (I'm thinking back to my stall days in early plat and dreading the possibility of my stall team needing to check TWO salamence instead of just one, or of trying to build a stall team where only one member holds lefties), that shouldn't be a huge problem if you're mostly looking for a casual, fun environment.
*Not to get all "competitive player" here, but I really have no personal problem regarding the pokemon I've listed, since they're all pretty easy to answer (although they have been difficult in the past, what with the physical/special spectrum being split by type instead of on a move-by-move basis making breaking skarm/bliss
insanely fucking hard), I'm only listing them because they're the sort of things a lot of wi-fi players dislike because of their tendencies to prolong matches and the fact that they're hard to predict around.