For this game specifically, I'd prefer pure single-character play and real-time combat. Party-based play should be minimal, unless it is co-op (which I'll save for another discussion). The Skyrim like companion system would be best, albeit with more depth and personality for the characters, and considerably better AI.
If for any reason CDPR chooses to go with party-based gameplay and non-real-time combat, I would hope for limited control over party members and slow motion over stopped motion. Limited control means you can shout commands (or give scripted commands ahead of time) and influence some of their choices in gear and weaponry (influence would rely on the players ability to persuade), but they effectively act on their own. Class roles and personality should also affect how these "recruits" act in certain situations. Slow motion over stopped motion is pretty straight forward, but the ideal slow motion would be similar to how GTA V handles it when players manage their weapon wheel or character selection. I honestly think that that is the perfect balance of slow motion and I wouldn't want it any other way.
To reiterate, I do want the game to have a single-character focus (and with real-time combat), but I think people should have the ability to "recruit" as many "helpers" as they can. Players should not be limited to one. There is no reason for that. Limitations should come from how the "helpers" react to the player, how helpers react to other helpers, whether they player has the money to pay for them or effectively persuade them, whether it be through blackmail or smooth-talking. I'd also like for players to be able to get assistance from random people off the streets. These NPCs would have talents, abilities, and personalities generated in a similar manner to how Watchdogs generates random NPC background info. Lastly, recruiting these NPCs would rely on a number of things including the situation, what the NPC knows of your character, your character's appearance (intimidating? attractive? unfortunate choice in skin color?), and your character's ability to persuade (through whatever means you have - threats, smooth talk, promise of reward). These NPCs would generally be pretty limited in what they can do, and therefor have fewer customization options (effectively none, compared to the established "recruits").
Also it would be cool if there could maybe be some unique recruits that can only be recruited through these random NPC events.