The idea is, to take select units from SC+BW+SC2 - and have them inserted into Diablo One; probably gotta rework the spells and stuff, but keep it simple, just spell books + leveling up, upgrade your “base attack”/abilities “spells” etc… Perhaps don’t allow massive units (in the tight quarters of the cathedral and the catacombs at least), and definitely don’t allow air units (except maybe a couple interceptors from say a High Templar, even allow two high templar PLAYERS, to meld into an archon and they have to share… and yes EVEN DTs into DAs) and before you say DT would be too op, since they’re going up against the demonic forces of Hell… They can see the DT because they can see their aura/psi etc etc or like “the hidden” can act as obs, and the scavengers could smell them and be detection too etc etc. The higher level demons down in the caverns and hell being conscious enough spiritually to sense the DTs.
Anyone feel free to contribute to this, vs some mamby pamby saying “Oh that’s a nice idea you have there, time to S#!T all over it, and kill your dreams…etc etc.” 
If we’re getting the big dogs involved (Blizz / activision / ms etc) they need to reboot the D1 world / game - IN VR / Augmented reality… and be able to swap out any of the blizzard franchises - except Overwatch! #Cringe. They all give off the vibe that they’d be fighting against the Lord of Terror, OW seems too “detached” from the other Franchises. I never really delved into the Lore/Story of Overwatch I’ll admit, I was never “into it”.
Warcraft they already have portals and stuff, and SC somebody could have opened a wormhole or something, or sensed the disturbance in “sanctuary” and decided to send YOU + Your friends to Tristram 
maybe if the world were to make any sense I’d categorize this thing Blizzard is going to ignore “properly”, even though I can’t because they’ve let D1 become “abandon-ware” in their “infinite wisdom”, and the answer is to make all the Diablo games after it not resemble the GOAT at all.