(Semi) educated guessing here.
If Paris uses the same format for the mixed relay as the WC and WR do (ie only one change allowed between heat and final), I suspect that might have an impact on the choices.
With the men's individual starting the day after the mixed final, the obvious change would be one of the men, to allow one of them to rest. However, the counter point to that is that the women have much more strength in depth. So swapping a woman would be less of a risk, in principle.
Both Dobson and MHS have had injury histories in the past that might make them skeptical of a 3 relay workload. However, they (and UK Athletics) might feel like the mixed is a better chance of a medal than the men's 4x4 is.
Obviously if someone else shows top form during the season (AHW or Rio Mitchum being the best options, Davey next so), that would make the decisions easier.
My gut tells me that we'll see only 1 of the two men mentioned earlier in the mixed at all and they might only do the final. I'd guess Dobson if I had to.
I think we'll see our prospective 2 strongest women, whoever it may be, in both heat and final. I say prospective because I do worry that Amber will not carry the college/indoor form all the way through the summer. History has shown athletes are a mixed bag in terms of whether they can do that.
For what it is worth, at the 23 WC, none of our individual runners took part in the mixed. In 2022, 1 did (AHW). In 2019 2 did (Yousif, Diamond). In Tokyo, none did.
But that's just all speculation on my part. I realise that I've not really helped clear anything up.