I am going to give some recommendation if you want to replace any of them.
Ludicolo: 4x resistance to water type moves and also takes neutral damage from ice type moves.With ability rain dish and holding leftovers,you can use giga drain,enery ball,surf and nature power.So,you won't have to worry about water types carrying ice moves.
Kingdra: also 4x resistance to water and takes neutral damage from ice type moves.
Mamoswine: If you want to replace torterra,this mon is perfect.Breed for icicle crash,has thick fat ability,and also has earthquake,ice shard for priority.
Metagross: It's a good replacement for gothitelle.With zen headbutt,meteor smash,bullet punch and hammer arm,it is really useful.
Blaziken: speed boost ability.Holding wide lens,with moves like high jump kick,shadow claw,blaze kick and bulk up it can be useful for Titania.But you don't need it for now.
The next gym leader is not Amaria.So don't worry about that.You already have pokemons to easily take care of the next gym leader.