Great question!

A few reasons.

it would add extra animation and hook ups. Time is a factor when we create skin packs. We do as much as we can in a specific window. Sometimes this means cool ideas just don't make it in. In the time that we did have we were able to put their bases in the character select and store screens so that's pretty cool.

It's also a single color tint for 3 different heroes and even though it would be really cool playing with the bases in game it means we would have to use the effort we would have put into something that might have more impact and use in game into something that would be very low impact. That's 3 sets of animations. We thought we could use an Animator's time better.

Another issue is that from a design perspective it had a potential to change the animation set so much that people wouldn't recognize any of the 3 skins as who they were suppose to be. This can be an issue, especially with 3 skins that could end up looking too similar if they were in the same game. Having them keep their default animation sets in game keeps their overall silhouette and recognizably higher than if they had a more homologous army man animation.

Thanks for the question!