As of now it is impossible to play Nomads in the regular campaign. Nobody is working on changing this. Also I don't know if this is possible (Nomads would need to be turned into a regular mod - but as far as I can see Nomads is no longer developed - so also I do not believe a Nomads campaign will come).

Setting up offline fa exe and then loading up the skirmish missions. Is easiest way. Then cheatspawning nomad acu. SCTA Mods also provide a means for this w/o cheatspawning!