I have my doubts that it's possible, but i'm curious. What is it that triggers your ability to recruit more than 1? Upgrades, right. Player upgrades. Anybody know anything about how the game handles those?
The game engine can definitely handle more than 3 followers. I altered the mission script function that adds followers to ignore the max, and brought 3 extras along into The Belgian Problem (the mission adds Pierce and Shaundi for a total of 5 followers). But getting the game engine to let you INVITE more than 3, well, that may not be so easy.
game_lib.lua has its party_add functions, which are used by mission scripts. One version ignores the limit, while the others don't. I changed them to be like the first. That's good for when missions force a character into your party, but doesn't help you invite more.
The unlockables.xtbl file contains the list of rewards, but the homie slots look like this:
Code:
<Name>HomieSlot2</Name>
<Type>
<Custom></Custom>
</Type>
<DisplayName>UNL_FOLLOWER2</DisplayName>
<Description>UNL_DESC_FOLLOWER2</Description>
<Image_Source>
<Filename>ui_reward_homie_slot_upgrade.tga</Filename>
</Image_Source>
<_Editor>
<Category>Entries:RespectLevels:Homies</Category>
</_Editor>
<Event_Text>UNL_FOLLOWER2</Event_Text>
<Category>Homies</Category>
<Detailed_Description_Text>UNL_DESC_DTL_FOLLOWER</Detailed_Description_Text>
<Price>12000</Price>
<Priority>HomieSlot1</Priority>
</Unlockable>
Notably, the "custom" type suggests some special code going on somewhere. So i don't think we can affect it by altering that file.
The code for the cell phone reward screen makes a call to cell_rewards_button_a in the mouse handler, as you'd expect from most of the cell phone menus. However, that function isn't implemented anywhere in code we have access to. That tells me that it's another internal function call, which means the game engine is handling reward unlocks in some special way, too, so we can't really mess with them.
So far, every piece of this puzzle has the game engine getting in the way.