Get decent tyres, properly line the rims with rimtape. Puncture proof tubes (flats at walking pace are fine. Motoredbike pace, not).
Change the front forks and rim with a disk brake variant.
Engineer some decent mounts for the engine, the factory ones are carp.
Get good lights so cagers can see you, you will be travelling faster than the average bicyclist, so they need to see you better.
Repack every bearing with a ton of grease, we tend to travel further, faster than normal, and the bikes are heavier.
That will do for a start.