I already successfully manipulated the dialogue, so potential followers will not refuse to follow when I have someone with me.
But when I ask someone to follow me, my current follower gets replaced by the new follower.
Example: If Farkas is following me, and I ask Aela to follow, Farkas leaves me and resets to his normal AI and Aela turns into my follower.
So my question is: What setting in the game determines the maximum amount of followers?
And how can I change it?
EDIT:
I have created a crude test mod that allows players to recruit up to 5 followers. It can be found here: http://skyrim.nexusmods.com/downloads/file.php?id=8559
Things changed by the Plugin:
* The dialogue that allows you to recruit followers no longer checks if you have another follower.
* I have created the aliases of Follower2, Follower3, Follower4 and Follower5 in the FollowerDialogue quest. These can be abused to have multiple followers. This must be done manually by the console however.
Press the Spoiler button to read its Readme
EDIT the second:
Foobar92 has created a mod that does exactly as I intended to reach with my mod, rendering my file obsolete. Please take a look at his mod here: http://www.gamesas.com/topic/1345602-wiprel-multiple-followers/
I am trying to create a mod that allows players to recruit more followers. Regrettably, its a lot harder than I thought, so I could not create a good mod.
So I started the following thread on the official forums to discuss it with other members: http://www.gamesas.com/topic/1344111-help-multiple-followers/ The member IMissLeeches asked me to upload my current attempt, so she could take a look at it. So here it is.
The current file only removes the 'check for existing follower' condition in the recruitment dialogue and adds some extra Aliases in the hope of duplicating the '2nd follower takes Dogs place' trick stated here: [src="http://skyrim.nexusm...ile.php?id=3758"]http://skyrim.nexusm...ile.php?id=3758[url]
If you know anything about this subject, please join the discussion on the official forums.
I have also purposefully disabled comments, ratings and other user input for this file to centralize discussion for this problem to one point.
The file itself
To recruit more followers:
1. recruit your first follower as normally.
2. Go to a another follower and recruit them. Your first follower walks away from you.
3. Now open the console by pressing the ~ key and type 'SSQ 750BA' without quotes
The console should say: ConsoleScopeQuest >> DialogueFollower (750BA)
4. Now click on your first follower and type 'ForceRefIntoAlias Follower2' without quotes. Close the console. If done correctly, this NPC now acts like a real follower.
5. To recruit a third follower repeat steps 2 and 3. But now your second follower walks away.
Open the console, click on them and type 'ForceRefIntoAlias Follower3'. Close the console. You can go up to 5 followers in this way.
Bugs and Issues
Listing whats NOT wrong with this file right now is easier...

* Only your last recruited follower will leave you alone when you tell them. The others will turn into permanent stalkers.
* It is not a proper mod right now, requiring too much console codes and user input right now.