All the mechanical disc brakes I've had (Spyke, BB7, Paul Klamper) require wheel removal to change pads, I've never considered it a big deal, by the time I've worn a set of pads down the caliper (And rotor) are ready for a good clean. The TRP's are the worst for a quick visual check, I'm not sure that plastic cover serves much purpose. I'm not a fan of TRP's brakes in general, the supposed benefit of two moving pads doesn't IME result in better braking and the complexity and miniaturisation to make that possible, compromises reliability.
On all my disc brake bikes except the folder, I've gone hydraulic. I hear the argument that they're not roadside fixable, but then neither is a TRP! I'm unlikely to ever be more than a taxi ride from a bike shop and if I were ever on that sort of trip I'd have chosen to use rim brakes.