Use two different crank arms. There are a couple different cranks you can buy in significantly different lengths, you suggested a 2cm difference. Origin 8 makes a couple cranks that come in a range of sizes so you can buy 2 sets, which isn't too expensive, say a 170mm and a 150mm. There will be some compromise in that you'll have a double or single chainring but they use square taper so you can adjust chainline with the right BB. Suntour offers a couple junior cranks that are 155 or 152, put a standard crank on one side and a jr arm on the other for a triple. Some cranks can also be drilled and tapped. It gets easier if you don't care if the crank arms match each other. Because the shorter leg gets the shorter crank you can set the seat where it should be for best range of motion on both legs, the shorter leg won't have to spin as large a circle and the longer leg gets the extension it needs to not cause knee pain.
I would not use toe clips and straps on a mtb that I ride off road, on road no big deal. A wide platform mtb pedal with pins will grip your shoes pretty good and might be the best solution for your feet.