Good question barnsey. I'd start with ebony timbermate. always looks a bit "husky" when you do that. but I found that the bondi blue still came out quite a brilliant blue after a few stain coats (but that was the look I was going for).
I reckon you got two choices, mix the black stump with bondi, like you said. I'd test that on scrap first.
or lay down a black stump first, then lightly sand back (1500 grit) and then put a bondi down. The spalted cap can handle it. the first layer of BS looks grey anyway. probably only needs one (maybe two) stain coats of bondi.
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