Definitely keep the DT hubs
Definitely get them rebuilt onto some nice, lightweight tubeless ready rims like Stans Alpine, or the new BOR rims, using some DT supercomp or Revolution spokes.
You’ll be looking at about £70 per rim, and £35(ish) per wheel in spokes. But then you’ve also got the 717 rims spare to sell on, so will be a superb upgrade for around £200 built.
Not really worth just using a Stans kit on the 717’s, the rims are giving away 80g or so each to a Stans rim, then the rimstrip you need to use adds another 50-60g per rim onto the wheel weight. Your 240’s on Alpine’s with DT Rev’s would come in under 1400g tubeless ready. As they are with the 717’s, then some rimstrips, they’ll be over 1750g ready to roll (I know, I used to have this same wheelset).
If you’re anywhere near Worcester, can give you a more accurate quote for the wheel builds if you wanted one?