>>4469583
Yes. Ballpark figures because nothing like this exists. We can use existic optics as reference:
>RF 24-105 f/4 has 18 elements, is closest to your FL wish, and is two entire stops slower
>RF 28-70 f/2 has 19 elements, and is closest to your requests for aperture but lacks the long and short end of your FL goal
>RF 15-35 f/2.8 has 16 elements, but more importantly has a objective element diameter of about 88mm
So, if either the extended focal range OR the bigger aperture requires just shy of 20 elements, we could safely say it would take at least 20. That's not absurd, but not a good start considering where we're going. The objective would also need to be roughly 88mm in diameter.

The objective element of the 15-35 would need to be made significantly larger, probably about a 15-20%+ increase of diameter to up the aperture to f/2, but to incorporate the UWA focal range you want (let's assume 18mm) you would change the groupings slightly so the FR doesn't go so wide.
Stick that objective element on the 28-70 f/2 lens barrel and extrapolate the trend of a bigger element down the line.

The trail-on effect means your mid-groupings are also much larger. But now we need to space them out and move them further apart to account for the 105mm tele and 18mm wide. We'll also probably need to add a few elements or groupings to account for the new projective distance and distortion on extreme tele and wide because our baseline lens didnt go so far either way.

All the extra glass and focal range means your zoom is pushing more material further back and foward. Oh and your MFD is also garbage, and focusing is slow as shit.

I'm skipping so much, but just this alone is already looking like a lens that is 1.5-2x the length of the 28-70 f/2, another 30-60% of weight, and likely will cost twice as much. At this point you've got a GP zoom the size and price of the Sigma 300-600 f/4 but you're doing UWA work with it? Christ.