Connecting an external control to a DPDT switch

Your basic problem is PNP1/NPN2. With the bases tied together, you are getting maximum current flow through the two emitter-base junctions from +12 to ground. Any real transistors in this configuration will die instantly.

If you must use BJTs and want to keep your circuit ideas as much as possible, replicate NPN1/PNP2, and use a fifth transistor to invert the base drive signal between the right and left sides of the bridge. Also, you'll need to either use a 12-volt coil voltage or provide a 6th NPN as a level shifter. But be aware that this will not work well, since the NPNs will not get enough base voltage to turn on hard, and you won't get very good performance.

A better idea is something like

^{simulate this circuit – Schematic created using CircuitLab}

You will have noticed, with some frustration, that none of the resistors have values. There's a very good reason for that: you haven't specified your load current requirements. At any rate, Q1 - Q4 are power transistors, able to handle the load current, while Q5 - Q9 are smaller signal transistors able to handle about 1/10 the load current.

From what you have described, you wish to press this switch into the on position, with some kind of device, just as you would by pressing it with your hand. A linear actuator would do the trick, but you would have to create some kind of cradle for it to sit in, and electronic circuit to control the actuator. I hope this is helpful.