Not to overstep, but basically the forum admin here won't talk about anything that's airsoft related. Admin just posts that thing about not using armor for airsoft and hopes you will drop it.
As nearly as I can tell, you're basically asking if it's ok to buy the kit and paint it/ do decals, weathering, etc. That would be perfectly fine, so long as you never talk about it with regards to airsoft.
We have a lot of people who build from kits here on the forum and occasionally you will see people refinishing purchased props and whatnot.
There's no rule that says you have to build everything from scratch.