I've always wanted to be able to do this in a oblivion.
I wanted a place where i could buy a mercaneries or 2 and have them follow me around. However unlike followers or anything like that i would want them to be completely expendable NPCs so i wouldn't have to care about them, and then you would be able to buy more when they died. A bit like the way you could have a apprentice mage follow you around or a dark brotherhood assassin but with more development on it and better tactic options.

Any ideas on how this could be developed or implemented?

Companions.

I doubt there will be mercenaries, but I think there will be some unique companions ,though I really don't want any of those. I prefer to play TES solo.

I want options for both named companions and hireable mercenaries with various different skills or alignments. Tes is a solo game, but its a lot of fun to bring some help along when confronted with a bunch of enemies.

It would be cool if your character gets some political status and has option of having a couple bodyguards tag along. However, I think max amount of followers should be 3 humanoid and 1 creature (not counting horses)