I'm not sure why you wrote this comment. Did you think that someone who did a PhD in this didn't consider this? The difference between writing this comment and actually trying it is why they give people PhDs.
Have a read of my thesis. I researched whether eval is used much (answer, yes). I looked at the challenge of inlining (you have to know what function is called - non-trivial). The naive jump-table thing you describe is basically impossible (or at least, it makes optimizing around it impossible). If you don't know the string value, all bets on all variables are off. You need to keep the value out of registers, you can't reorder operations, you're basically at square one.
Have a read of my thesis. I researched whether eval is used much (answer, yes). I looked at the challenge of inlining (you have to know what function is called - non-trivial). The naive jump-table thing you describe is basically impossible (or at least, it makes optimizing around it impossible). If you don't know the string value, all bets on all variables are off. You need to keep the value out of registers, you can't reorder operations, you're basically at square one.