Supercharging is a good route. Lots more history as to cost, performance and installation that can benefit you.

No updates, we're busy with less interesting things, only the gearbox is there.

And the engine has to get a dry sump lubrication, since it allows us to use a simple design oil pan, to play with the stock lubrication would be to risky IMO.

However, my estimates about the date of accomplishing were too optimistic it'll need at least 2 years.

The right way to go.... IMO.
BMW X5 4.8i S Performance Parts - Dinan

You mean dinan will be able to turbocharge the 4.6? No way.

Dinan offers no turbocharging 'kits' for the X5 or any other models. They do offer upgrades to current models already turbocharged. They offer a supercharger for the 4.6. As I recall, OP was going to go with supercharger. If still going that direction, might want to reference what Dinan has in their kit as it was dealer installed, frequently on a new X, and Dinan supplemented the dealer warranty.