As I said before this is a very personal selection and one where money has not really be considered so more a flight of fancy with the more expensive choices.
A studio gives you controlled conditions, heavy cameras are not an issue but large maluble files useful for post production are essential.
High on the list must be the Sony A7RIV at 61 MP full frame 35mm sensor its a technical tour-de-force, up there must also be the Nikon D850 and Canon 5D. The new Leica SL2 must also be on the list.
As this is the studio then lets think big and consider medium format.
Lets first consider the big players; Hasselblad and PhaseOne.
Your talking big money, and even though this is a flight of fancy. While a bottom of the range Hasselblad H series starts around £14,000 and for 100 MP its over £30,000, lets me a little more reasonable and consider the Hasselblad X and the new Fuji range.
The new X series Hasselblad, the X1D II at a little over £5399 is quite a camera and the colour is unmatched, the flash sync up to 1/2000 and a degree of weather sealing should one want to take it out.
The Fujifilm GFX range has really set the world alight. A, for medium format affordable system. The S and R have the same sensor as the Hasselblad X, an older sensor without the outstanding colour of the Hasselblad but the price is hard to beat, but a more limited flash sync. The R at under £3,000 and the S at £4500 are tempting in the extreme, but the new GFX 100 with a newer sensor at £9500 is outstanding.
What would I pick, a tough choice, it would be between the Leica SL and the Hasselblad X. With my previous choice being a Leica, being able to have the same lens mount between the two would make life easy and its a very modern sensor compared to the Hasselblad, but the draw of a medium format lens and the advantages of the bigger sensor is tempting.
I think I would pick the Hasselblad.