Could someone check this diagram please?

[Simon Barden]

Yes, you could do that. You'd definitely have to wire the volume pots as you've shown in your first wiring diagram (except with the order reversed) so that the pickup output wire goes to the middle tab/lug (the wiper), and the pot output comes from the end lug, rather than the more common wiring (for most guitars) where the pickup output wire goes to the end lug, and the pot output comes from the middle lug.

Otherwise you'll kill all the selected pickups output when one volume pot is turned down as the common output will be taken to ground through it.