Dimarzios in a Fender Marcus Miller JB?

Depends on what you consider a “good idea”...

The tone will certainly change. Whether it’s a positive change or not can be determined only by you in the end. The only thing anyone can realistically assure you of is that the tone will certainly change.

 

Or Ultra J's depending on what you want to hear. The Model J's are a little dark for my tone goals though they might be perfect for yours. Ultra J's are brighter but still have good output and low end. I would think they would play nice with a preamp since they are similar to Sadowskys.

 

I'd LOVE the Model Js in a Marcus. Those are my fave pickups anyway, but they would kill in that bass. So if you're taking a poll, I vote YES!
(and in CREME, but that's me...)

 

Here's what mine sounds like. I'll leave it up to your ears to determine if they are scooped or not.

 

Ultra Jazz pickups and John Easy preamp
Fast forward to 8:55 for playing examples

I have a set of the 5-string Miller Signature pickups, and they are quieter than my Squier VM Jazz V pickups (odd because they are 8.0k ohms and the Squier pickups are 7.5k ohms), but they do sound really good. I will eventually be pairing them up with a boost-only 2-band Pensa preamp.