Just thinking out loud as I’ve got a set of old, but little use, DeeMax wheels and thinking of getting some 33mm LB rims to go on them as the hubs are in perfect condition.
The current spokes are Mavic’s own straight pull so can I just use any SP spokes that are the right length for the new rims?
I’m thinking that, as the hubs are 28 spoke, they might build into a nice light wheelset for normal, AM, use..

Assuming they’re standard SP spokes (I know they’re not the fat Zircal ones, but it’s not a given), then yes, theoretically that will work. Finding a good supply of SP spokes isn’t that easy though, and they’re a bit of a bitch to work with. Considering Mavic hubs aren’t all that either I’d just sell the Deemaxes and buy new.

just sell the Deemaxes and buy new

That was my other option

Do that. Far far less faff, and there’s nowt special about the Mavic hubs.