Do you guys think it would be good if you could "un-research" the supply techs maybe? How much should it cost, and what other penalties, if any, would be needed to make it fair?
That's exactly what I was suggesting and where 'realism' is concerned, I think it would be far more realistic that way. If an empire isn't using facilities related to maintaining X number of ships, why on earth would it continue to allocate the resources to support them? There's nothing stopping a 'real' empire from mothballing or reallocating unused facilities. It happens all the time.
As for how to balance such things, I honestly doubt this is even being considered but if it is, that's something I'd leave to the experts. I see no reason that it can't be done or how it would devalue the strategy of this game. Every player would still have decisions to make regarding when and when not to build up and draw down. They would just be making decisions about a different set of variables.