Why not try and add Dumba to Enroth, Dumba has good value and I'm sure you can pick up another D prospect. You could also push Winnik onto them, he's had a hot start and maybe they might buy into that, his production will taper off eventually.
It seems like the lehner owner is not to willing to trade him. I'd start with a relatively low offer on markstrom and build from there. I think long term these two young goalies are fairly even but Markstrom has the easier path to a starters role.