
The block itself disable physics between that 2. The mergeblock works fine for 'modules' ideas (hydrogenengine, ion-boosters, Batteryarray.) but not sure for temporarily connections as they get random name on disconnect (new grid will be generated from disconnected blocks).

Because of the torque and displacement settings on rotors (and the way they appear flexible about these in a way that pistons are not) you can merge as many rotors together onto a single joint as you want (within reason). This mod can be a 'proof of concept' to make it Vanilla version. The game engine doesn't appear to be able to handle this at the current time. When you add more points of attachment it becomes rigid, and the piston synchronisation needs to be perfect. When you attach a door by 2 points, (or a platform by 4 points) it allows a degree of variance in the piston positions.

However there is enough variance for the game to care about it. On the right I used a rotor to try the same and on the middle I used a piston. They are close to perfect, and you'd be hard pressed to tell by eye. The large hydrogen thruster on the left is built on a hinge and has a merge block on one of its sides.

The pistons are not 100% precise when they move. But even if it does work, it seems to cause problems over time with use - mostly broken pistons and deformed blocks. Sometimes it works for me, sometimes it doesn't. I've always had problems merging more than 2 pistons on a door or 4 on a platform.
