I had the same idea earlier this year but from a standard 130 BCD 5 arm Quarq Dzero with GXP spindle rather than the dfour. I got in touch with Quarq/SRAM and they told me the new DUB crank arms were not compatible with the spider I had and replacing just the cranks for a shorter length on my Dzero was almost as much as buying the new AXS/DUB spider and cranks separately. (Might be different for the dfour so I’d reach out to them before buying anything).
I ended up selling my old PM and replacing. I was using an outboard Wheels MFG on a Specialized Allez Sprint and had to change the whole BB. I’ve been using the SRAM DUB BB for BB30 and so far it’s held up well. Better than my previous experiences with SRAM gxp BB’s in typical British weather.