Well put. Since both modes lend themselves well to different situations, why not come up with combat that lets you switch them on the fly? If balance is an issue, you could disable certain things/abilities and add incentives to prefer one to the other depending on the context. Again, it doesn't have to be a tabletop simulator.
A compromise like this often leads to either one or both being sub par. Two examples: Arcanum, which was a complete failure in that regard. Neither TB nor RT worked well and combat was the worst part of the game. Then there was Fallout Tactics, which actually pulled it off although you really had no reason to use real time unless you just wanted to dispose of a trash mob quickly.