The exhaust system support looks good.
I agree the appearance of a natty roll bar is an important part of its appeal, especially if you have a tray on the back. You could even put lights up there on top of the bar. It is an important safety feature as well, even on smooth ground. Sooner or later some kid may get on it and do something dumb.
If you are staying on smooth surfaces, I don't think bigger wheels are all that good an idea unless you widen the track, and that is likely to overload the steering kingpins, which are usually pretty marginal on ride-ons to begin with.
Personally I think over-riding the engine's governor is a terrible idea, it just throws away the reliability of the Briggs, which is one of the machine's best features IMO. I also think you should keep the speed down to 5 mph maximum - you are much less likely to hurt someone or hit something expensive. That machine just does not have the stability or braking to go faster.
