Construction of the drywall partition for a washbasin in board form

Tomorrow :)
I am currently planning the drywall partition for my bathroom.
A board about 2.5m wide is to be mounted on it as a washbasin counter, on which the countertop sink will then be placed:


How do I best build the drywall partition here so that I can securely attach the crossbars that are supposed to hold the "board"?
Are standard 100mm CW profiles sufficient here, which I equip with a 22mm OSB3 board onto which one layer of drywall is then applied? (Sink weight approx. 50-70kg)
The prefabricated elements for washbasins, e.g., from Geberit, are less useful here, as I cannot do anything with the pre-installed threaded rods there.

Unfortunately, a DN40 drain pipe from the sink to the right exterior wall must also be routed through the vertical studs.

Do not attach the boards to the drywall elements themselves, but to a frame that supports this drywall. This is easily ensured with a wooden structure (similar to a mounting frame for a hanging toilet).

I had originally also thought of a complete construction made of wood. Until I saw the prices for glued laminated timber beams.



But you mean only building such a beam frame in the 2.5m width and about 1m height, and then constructing the rest again with "normal" metal drywall profiles?

This is how I would build - however, not with glued wood, but with plain [KVH]. Then it is not expensive and the whole thing can be processed wonderfully.

Wouldn't that warp over time, causing cracks (especially on tiled surfaces)?

That is state of the art. There are no cracks. Provided that the wood is dry.