Why not make two separate kernels then?
VECTORS4 might one day be the better alternative, instead of doing all that work then why not start now and keep pace?
Because I have literally put in over 100 hours on the main kernel and have gotten almost nothing in donations. I just don't have the time to keep up with two kernels. If anyone feels like making a VECTORS4 branch, go for it... the source code is in the public domain and you can use how you'd like.

Also, from what I've gathered, there may be only 1 or 2 people interested it... If you can lower your memory speed, I think VECTORS will always be faster than VECTORS4.
Now, I do like hearing feedback from everyone. I am just letting you know that it is not feasible to optimize the kernel for every possible configuration (SDK 2.1, 2.4, slow memory). Right now, the kernel is optimized for SDK 2.5 and the 68xx and 5xxx cards and assuming you pick the best memory clock speed for your card (somewhere around 1/3 of your core clock).
-Phateus