Daddeooh!
The vast majority of ebikes, as far as I know, have disc brakes. Hydraulic disc brakes were a must for me when I first bought the Roam 3 - and I had no real knowledge of ebikes at that point. I'm 200 pounds, and with the added weight of the motor and battery, I'm glad I have hydraulic discs, and as I mentioned, I replaced the stock 160mm rotors with 180mm rotors. I also recently installed sintered metal brake pads, and I'm happy with them so far.
You are right that mid drives put more stress on the drive chain, and can shorten the life of the components. But I have already changed out the chainring, chain, derailleur and cassette when I converted from 2x8 to 1x10. I'm sure I'll be able to handle any replacements if these parts wear out.
But one advantage of mid drives that I rely on is - occasionally I have to make a quick stop, we all do. If I'm riding in 5th gear or higher, and then stop, I find it very hard to get started again in that gear, even with pedal assist. The rear wheel has to turn in order to shift down, so what do you do? Well, I'll shift down to 3rd gear, lift the rear end up slightly by the seat stay, and give the throttle a little touch. Shifted!
And I still look at the MANY ebikes now available online, some are unbelievable! The one that has me drooling at the moment is the Sondors LX. It has fat tires, 750W mid-drive motor, step-thru (which really appeals to me), and just looks super hot. But, it's $2300. Maybe someday, huh?