After experiments in switching to using BANK memory instead of arrays proved only that there was no performance benefit - perhaps even a deficit. Thank god than that I'm writing my code on my Mac and am able to branch and commit into git.
I was testing with 9 mummies, and even inlined the code (removing the PROC calls), but it still went too slowly. So back to the drawing board.
This work makes me also think about my day-to-day (paying) work, in how can I simplify my code either to optimise for maintenance or optimise for browser speed (and thus, a better user experience).
It really doesn't matter how the code looks under the hood, so long as it's good for the user, the player, the visitor, the person who actually uses the final product.