Oh yes I do believe that this is called engineering
I like that by going for 1/13.5 you are close enough to 1/14 to take advantage of products that are available off the shelf such as Tamiyas wheels/tyres.
I will continue watching this fascinating build with great interest.
My friends have a light and siren control system. The siren has 3 possible sounds and can be switched during operation. Used arduino nano and wt588d module. I think he'll like it.