I agree with 350htrr; if you want to go 35+ mph on or off road you'll need to have something like what Hi-Power Cycles sells and be prepared to spend extra money.
I'm curious to know if you've gone 35+ mph on your current Marin Mount Vision Pro on and off road?
The other concern is how far do you plan on traveling at 35+ mph? The amount of batteries and their weight will set you back if you plan on going anything more than 20 miles. In addition, the stress on all the components will be that much greater.
I've hit 36+ mph on my bike but I don't see how I could do that off road. I would certainly make sure my health insurance was up-to-date and that I had full coverage.
The faster you go the less time you have to react to what's on the road and off road a little twig or bump will send you flying...literally.