While lighter is possible with alloy rims this set of Mavic Open Pro UST rims 24F/28R laced to Extralite Cyber Sl2 and Cyber hubs with Sapim CX ray spokes has a mass of 1293g. That for a 24mm wide alloy clincher rimmed wheelset with a decent spoke count. 

Stans Alpha 340 rims would be lighter but they are crap rims. Tubeless tyres fall away from the rim without air making them impractical in the long run and tubed tyres dont always stay put at 100 psi. Kinlin XR200 rims are not tubeless compatible and are very narrow at 19mm wide. So these rims dont really meet the needs of customers anymore. 

Mavic Yskion UST II tyres have been fitted. They look like the previous version and the previous version is fine, I  that they grip well and are comfortable. Puncture resistance is fair and the hold air well being a UST tyre. They weight a claimed 260g each. With tape valves and tyres mass goes up to 1022g rear and 900g for the front. 

They are reasinably stiff (compared to the wheels I normally build), light practical wheel. The hubs may be sub 200g for the pair but if you smear the supplied grease or equivalent over the freehub mechanism and a marine grease over the bearing seals you will get good bearing life. The hub maintenance is minimal and they require no special tool to maintain. 

So if you want light and practical then get in touch. If you want the lightest clincher and sod practicality/reliability  then there are other wheel builders. Although I build carbon tubular rimmed wheelset under 1000g. Those are proper light and I think tubs are practical.