HP-UX and to a lesser degree AIX had some of this. Instead of just static tunable values there were some tunable formulas exposed to the admin. If one knew what they were doing they could change the formula as needed without having to recompile the kernel. I would not mind something like this being exposed from the Linux kernel as tunable options as opposed to just static values. Such options could reduce the number of companies that need to recompile the kernel.