I’m tempted to buy an SLX 4 pot caliper and stick that on the front – Shimano levers and calipers are all interchangeable aren’t they?
Not really. There are 2 different hose types. BH59 and BH90.
Your M410 uses BH59 and SLX uses BH90. You can get M420 calipers which are 4 pot and use the BH59 hose. I’m not sure if they give you the bleed nipple or not though.
If you get the a complete SLX brake, it’s east enough to fit the front.. The rear will probably need the motor and battery removing to pull the new hose through, it’s pretty tight in there.
Deore 6120s give just as power as the M7120s but use standard pads rather than the finned ones. M8120 are the same but have a nicer finish.
I was lucky with my Rise, it’s came with M6100 brakes so I just stuck some M6120 calipers on there.
If you’re going for different calipers, I’d get some different discs too, the standard resin only ones are a bit crap. In fact even if you’re not changing calipers, I’d still change the pads and rotors.