Jolteon is the only good Eeevee. I f you want an Eeveelution get a Jolteon (but that Ampharos though)
get a Donphan instead of a Mamoswine (don't need two ice types)
get a better flying type (like a Crobat, don't underestimate the Zubat line, Crobat is amazing)
Ampharos, good choice
Lapras, good choice
Typloshion, good choice
You should probably get a better dark type (like a Tyranitar)
and here's a challenge. When you make it to Kanto, make a whole new team, put the team you used in Johto away in the PC and use new team of Kanto Pokemon