There are 2 ways to go about what you are looking for-
1. You could swap the volume and blend pots for 2 push/pull volume pots. If there is a blend p/p pot, that would be an option as well.
2. You could leave the preamp as-is, and add 2 DPDT switches for coil tapping.
If a pro is doing it, they'll probably know what can and can't be done, but those are 2 options I know will work. I went the route of 2 switches for a project bass I have- each one controls series/parallel, and they come in handy sometimes. just be aware that there is a volume difference between the 2 settings you will have.
Thanks for the quick reply. To my understanding, the TWs come with the volume p/p pots...so in order to go through with option 1 all I have to do is order a pair of the pickups, correct? Sounds like the simpliest method to me.