Is it possible to use uncoupling magnets with Bemo (as opposed to Greenwich) couplings, or would ramps/wires be better?
I think the problem lies in them needing a "push up" rather than a "pull down" due to the position of the pivot and the decoupling lever arm. It may well be possible to add an arm in the right position and angle but it might take more effort, time and be less reliable than swapping the coupling, especially now there is a version of the Greenwich coupler for fitting into coupler pockets.
I have done this, but agree with Graeme about the time, effort and reliability, so would generally not recommend it.
Perhaps using some sort of lever or ramp would be better after all, as I don't have time to swap or modify all the couplings at the moment. I would usually just use a manual uncoupling hook, but since the loco on this layout will always be uncoupling in the same place, I felt it would be quite nice to make it hands free.
I started off with Bemo style couplings, but then converted to Greenwich to enable remote uncoupling. However for things like rakes of coaches, I only changed the couplings of the end coaches as the rakes remain coupled all the time they are on the layout.
Frank