is it iva compliant to fit a transmission handbrake as opposed to dual action callipers??

Yes, a drum on the prop like LR Defenders would be fine. It needs to be a proper brake that works when moving though, not just a locking device like an auto tranny Park position.

great....a way that i can fit 6pots on the front and 4pots on the rear

Save yourself some money and fit four pots on the front (if you must) and two pots or swinging calipers on the back. Not as if you are trying to stop an ocean liner!
Cheers, Pewe