I'd be stoked for an open world Splinter Cell game - so long as they get the stealth right.
I am fine with the lack of visual variety in the setting for FC5 - but like you say, a faction based wanted system could do wonders for making the game as busy or not as you want it to. That said - mission to mission I am having tons of fun and the stealth works fairly well for the outpost missions.
The game definitely empowers the player right from the get go - even though I have died lots, I have never encountered a situation yet that I didn't feel I could beat with the tools available to me. I would love to see a mod for it that drastically reduced the random encounters - but also put the player at a severe disadvantage (slower walk/run speed, weapon degradation, limited ammo reserves, higher buy in on prestige weapons/outfits, perks unlocked slower, etc.). There is enough of the game both in missions / extra activities and world exploration to support a slower more survival based experience that the setting kind of touches on before going full action movie within 30 minutes or so.
As it stands though - it is a blast to play and most of the gameplay mechanics are spot on.