Am I allowed to skateboard in ACU's, more specifically on a boosted board, as a mode of transportation?

It depends..
If the local commander (and every other service members that sees you on one) views it as a toy for recreation, or a transportation vehicle.
If its viewed as a toy, you would likely be held to the same rules and standards as you would any pother skateboard. Likely there is post or garrison policy on use of skateboards on post.
If it is viewed as transportation the problem will be, its so new as such, there likely is NO policy to guide..so folks that have a duty to correct, instruct, inform or guide you will do so based on personal opinion...and a legal order is just that. With no written policy to fall back on... you must follow the orders given you by all those that out rank you.

My advice... offer the command something BEFORE they have to write post policy on "power motor assisted skateboards"

Write the policy yourself and forward it though your chain of command for review and passing on to the post commander.
In this way you get the policy you want, not the policy some Corps or Div G3 SGM wants.

Id suggest taking a look at the use of bicycle policy, and in general mirroring it.

Just to tack onto this conversation, after reading everyone's response, would that mean Service Members can use a hoverboard as well as long as they have the correct PPE? What about a segway device?

Wear proper PPE