It looks quite well done for the project. It's not useful for competition, but it looks good anyway.
Nice render too.
For the top shaft of the gearbox, instead of using a hex bearing, I would round down the end of the shaft and use a round bearing.
If you only have 2 standoffs going to the mounting plate, I would change it to 3-4.
EDIT: +1 on the PTO idea.