Basic has commands converting between types of numbers, but they are rarely used because compiler does it for a user. It checks for type and then converts if it's necessary. I think if you add an additional switch to the compiler, e.g. -strict or so to force the user to take care of the variable types and conversion, it would give speed boost for compiled programs. I heard that some programming languages use this and it works.
The second - afaik freebasic compiler "sits" on crt that way or another and all the discussions about speed boost ends up in "use crt". What if replace freebasic internal procedures with calls to crt? The first fb compiler afaik was created to demonstrate that writing something like that is just possible, but now it is a mature programming language and if compiled programs need crt to work, compiler's own procedures can be replaced with calls to crt. This would also speed up program's execution.
I'm not a good programmer like The Great Ones from the forum and I can be wrong, just a bunch of thoughts.