If the pay model is "pay for the character you want or use the one we are offering this round, which is technically just as good as the others," then I can see that as being a great model, especially if combined.
On the skins changing something small. If it is truly trivial then maybe, however such things tend to stack and even a slight move is still a move and thus can be called out. However such things would hardly be the worst part of DOTA/MOBA design, indeed such games seem to be built around bad design even though they do not have to be. My favourite one was probably when some people were defending, to the hilt no less, the need to have the option to kill your own (hopefully near dead) towers to deny experience to your opponents.
On the skins changing something small. If it is truly trivial then maybe, however such things tend to stack and even a slight move is still a move and thus can be called out. However such things would hardly be the worst part of DOTA/MOBA design, indeed such games seem to be built around bad design even though they do not have to be. My favourite one was probably when some people were defending, to the hilt no less, the need to have the option to kill your own (hopefully near dead) towers to deny experience to your opponents.