It's all subjective and individual. I love playing NES, Atari 2600 and N64 on my 13" RCA from the 2000's. If my Commodore monitor worked better, I'd...
Just like with cars, there is a market for original/unrestored, restored to factory spec, AND upgraded/restomodded examples. A properly-done console...
Even then, that'd be in the eyes of the buyer. If I had the liquid money, I'd rather have the Ben Heck repaired Nintendo Playstation rather than the...
For a legitimate "rare" console - I imagine mods would lessen the value. However, it would have to be rare. For just basic older consoles, I am 100%...
It really depends on the situation, there's plenty of common failures where some mods are needed to actually repair an item as there are high failure...