Or, get two forks for your MTB/off-road bike. One suspension, and one rigid with low-rider braze-ons. With a cartridge headset like a Chris King they are easy to swap out in just a few minutes. Put a second CK fork crown baseplate on the "spare" fork, along with a second brake. Easiest to do this with V-brakes, but you could also do it with discs.
I have my 26" Co-Motion set up like this, with a Rock Shox suspension fork and a rigid fork from a Surly LHT. Great do-it-all bike (it even has S&S couplers)!