Scrypt-jane doesn't mean it has a variable N factor...could be fixed and it would still be some form of scrypt with chacha as mixing function.
in practice most jane coins are just forks of Yacoin, copying the formula for progressive N and only varying the start time and possible the nmin and nmax parameters.
In my opinion, all these coins progress too slowly to really fend off ASICs in the long tern...
Christian
Only way I can imagine it being feasible is make an asic with more than enough ram for a few n factor changes and then add more ram for the next gen.