It's pretty inexpensive to upgrade to hydraulics on your own anyhow so if that was the only difference holding you back then I think you made the right choice.
You can get a complete bolt on set (master/slave levers, pre-bled with fluid), the only trick is that you need something either made for ebikes(pricey) or modified with a cut off switches added. I got a modified Shimano set for $110 (+ some nominal customization fee since I needed a longer rear brake line) and it works great, although it did take a couple weeks to arrive.
If you are technical then you can save even more by buying a non ebike set but adding your own switches...?
Thanks, hewstigator - where did you get the modified Shimano set - were they for a Ui6 & were they for both front & back brake w/cut off switches for that price, please? Also - how difficult to fit, please? Thanks
I installed mine on a Specialized FSR - but they seem to have the same standard mounts as my Surface604 Colt so I suspect magnum is similar (maybe to verify just measure the bolt to bolt spacing on the frame / shocks).
Amazon.com : M355 2019 Modified Hydraulic Disc Brake(Can Cut Off Power) for e-Bike DIY Conversion Kit Parts : Sports & Outdoors
it was ridiculously easy to install since everything is already connected (the levels, brake lines, slave calipers). it involved unbolting the originals, and then bolting on the new ones with some zip ties to manage the cable routing. finally, plugging in the brake cutoff switches. that price included both front and back BUT i had to add a customization fee (i forget exactly how much but i think it was around $20) for my custom rear brake line length - you need to measure both your existing front and rear brake lines to see if the default brake line lengths will be ok...
as alternatives, if you are going the home-brew route there are also bafang magnetic cut-off switches you can add to many hydraulic brake systems (but not all, you need to see if the brakes you have in mind will work with these switches, as well as the grin tripwire which should work on any brake system since it comes in both a push and pull variety.
PS the modified shimano set I got from the aforementioned seller worked great BUT when the weather dropped below freezing there was a point at which one of the switches would get stuck in the "brakes ON" position - somehow it managed to loosen up after a little while, not sure if it was because i hit it with some oil or it just normally worked itself looser? it works great now...