At first you asked about other ways to speed up batch files. Considering that TCC or the OS must do a lot of reading (ultimately character by character) and a lot of hunting for matches through names of aliases, commands, and variables ...
1. empty the environment all you can
2. empty the alias list all you can
3. use short variable names (one-letter ones are the best)
4. use multiple commands on one line (&-separated) as much as you can
All that makes for ugly batch files, but I've tried it in Monte Carlo probability simulations and they make a big difference.
A question for Rex: When trying to match the name of a function or command what kind of search does TCC use ... linear ... binary?