tacky depends on the setup, consider a tank near or in a nursery, in the lobby of a family practice doctor, or for some of the bigger kids like myself who happen to have a ton of lego's. I've got a shelf full of lego builds that I've done in the back room (where I build my legos with my nephews). I think it'd be a perfect addition!
go a step further and find a way to build framing and hood out of lego thus making it an honest to goodness "lego tank".
I hope you follow through with this, I would love to see it!