That's the other option. Not buy any lenses, and either buy new or buy a second hand Z5 somewhere early next year.
The 24/70, 50mm 1.8 and a 28 2.8 seems like a really nice 3 lens setup... But most likely I would want the 24-105 S when it comes out. That's the perfect lens on a FF body for me.
Look at a Z6 used, in the UK in dependably "like new" condition they are slightly less than a like new used Z5.
You're not going to make your lens and stabilisation needs fit with Nikon DX, without clunky workarounds. My instinct would be to just bite the bullet and go FX now.
Nikon hasn't bothered with "premium" DX lenses because they have FX lenses competitive with premium APSC and m43 lenses. What I mean is that FX zooms like the 24-70 f4, 14-30f4 and 24-200 are not really bigger, heavier or more expensive than the premium equivalents which are f2.8 in APSC and would be f2 in m43.
For example, if you bought the Fuji X-H1, you could get the 16-55 f2.8 premium zoom. But that's slightly more expensive and meaningfully larger and heavier than the Z24-70 f4S. The Z S lenses are all pro built and weather sealed, they are not consumer kit lenses.
Take the WA zoom example. The Fuji 8-12 f2.8 is equivalent to the Z14-30 f4. Except the Z is smaller, 60% of the weight and is 65% of the price - the Fuji is a $2000 lens vs $1300 for the Nikkor. The cost delta in just this one lens is more than the cost delta between a Z50 and a Z5. That's why Nikon haven't bothered with premium DX lenses. It doesn't make sense, it's too close and adjacent to the FX line.
Don't get me wrong, I think Nikon should have a handful more DX lenses - a compact WA zoom and a couple of native DX primes with VR (the 28 2.8 looks nice but it's too big and slow for DX in my view), but not premium zooms and primes.