The problem is that even if you manage to get RInc=0 after launch, the LAN precession during waiting in parking orbit means RInc=0.05 at the time of injection into transfer orbit... Hence we end up doing an off-plane intercept if we want it or not...

It's probably because I'm a noob, but I don't understand why off-plane intercepts are a problem. A RInc of 0.05° means that if you intercept at one of the nodes, your speed relative to the other vessel will be about 7 m/s. And the maximum distance between the two orbits (90° away from the nodes), will be about 6 km. I've just been using Sync MFD as follows:

1) Starting from launch or from a parking orbit in a near-correct inclination, push out apogee until it just touches the target's orbit on Orbit MFD.

2) You want to eventually get intercept at that point, which will either be your apogee or perigee depending on whether the target is ahead of your vessel or behind. Ex: If it's ahead, you'll want a smaller orbit than the target so you can orbit faster and catch up, so the intercept point will be your apogee.

3) Set up SyncMFD with the correct target, set Len to 10 or 12 and set the mode to Ship Pe (target is behind your vessel) or Ship Ap (target is ahead of your vessel.)

4) At apogee, burn prograde to raise your perigee out of the atmosphere. If the target is behind your vessel, you'll want to continue burning until you raise your apogee above the target's orbit. (If the target is behind you, you want to orbit slower than it so that it can catch up. So you need a bigger orbit than the target.) Then, using low thrust, burn until you get a DTmin that's low single digits.

5) Then, a full orbit prior to intercept, re-adjust using either a retrograde or prograde burn until DTmin is low single digits again.

This should get you at most 20-40km from your target at closest approach, at which point you turn on the docking HUD, kill relative velocity and then burn toward the target. (It's possible to do a more efficient approach by vectoring your relative velocity toward the target instead of killing it, but this is more complicated.)