I doubt you'll find a 29er pro4 boost wheelset at 1500grams. Lightest in the fortus range is the 23 which is 1850g. That light you must be looking at carbon rims. Spendy spendy.
I'm not sure which is the Hope race XC, but ive a new pair of X2/E4 calipers in purple and a new pair of Tech3 levers in black with purple lids. Front is made up, but the rear requires a hose. Could do them for £240 or with vgc 160/180mm purple floaters £300 =-If you get brakes/rotors I'll chuck in a pair of clear braided hoses. Used but in good as condition.
I recently built myself some 29er wheels, 32 spoke, using Sapim Laser spokes, Ryde Trace 25 rims (which i have a few sets of and i love) and fairly basic 6 bolt novatec hubs. Wheelset weighed in at 1550g. They're lovely wheels to ride as the rim is very shallow but wide enough to keep the wheel stiff. Just a thought.