Skyrim was so easy because all followers had the same basic follower dialogue, and just by selecting certain voicesets when creating the character will open up all follower dialogue for them.ĮDIT:- Oh yes, if you don't mind the followers not speaking when you talk to them, and not actually being dismissable to anywhere other than where they spawned, you can use the console to add pretty much anyone as your follower. It's not so much the problem of the voiced protagonist, though - the NPCs are going to have to have lines extracted from their existing dialogue to make things work anyway, and anyone willing to take the time to do that will do the same for the voiced protagonist's answers.
I tried creating a follower in FO3, and just gave up halfway because it was quite hard to make it work, and just relied on the Nexus. It's much harder to create followers or make existing NPCs followers in FO4 than in, say, Skyrim, where anyone and their mother-in-law could create a follower (and the Nexus is full of heavily modded sexy female companions). I'm hoping that those talented modders who created all those FO3 and FNV mods will make a return and mod some followers.