The only standard contact is the "hot" one, the central one. All the rest is proprietary and is not guaranteed to remain the same even within the same maker products.

There is a solution to your problem.

Many, many years ago German flash producers (Metz, Braun, Agfa and others) agreed on a standard for dedicated flashes which is called SCA.

You buy a SCA-compatible flash. Then, you would buy a SCA adapter which would adapt your SCA flash to work as a "dedicated" flash with your camera(s).

The first generation had 3 figure numbers. E.g. SCA 310 was the adapter for Canon A-1, SCA 311 was the adapter for Minolta dedicated flash (including TTL function for X-700 and family) etc.

Subsequent SCA flashes using 4 figures were adaptable to new-generation AF flashes (which dose light emission based on autofocus, or assist AF with a red light, etc.).

Somewhere on the internet you should find a diagram with all the SCA codes.

So you could buy a SCA flash and an adapter for Minolta TTL system and an adapter for ME Super flash system (not TTL if I remember well) and, by only changing the adapter, you can have a dedicated flash which will work just like the "original" one.

You can also find an extension cord. You place the adapter on the camera hot shoe, the extension cord on it, and the other end of the extension cord to the flash. You only need to buy one extension cord and you can use it with whatever SCA adapter and SCA flash.