That nextie set looks nice!!
custom build is the way to go with requirements like this. I have build a 50mm / 23mm wide (internal) set that weighs 1360 grams… (around 1000 euro) With some more budget, you can get sub 1300 very easy.
(more details here How do you feel about the current Carbon Wheel market? - #46 by nvalphen).
fancy hubs, fancy spokes and you have some room for a deeper rear rim
for the MTB I have Duke rims and hubs, also very nice road stuff!