Disclaimer: Playing with real people is usually more fun and sometimes more successful. Like any hireling they would not be allowed in raids.

For x amount of TP you could buy a custom hireling by level (1-20). You could purchase as many custom hirelings as you want per level.

By level and class, you would choose what the hireling has on it's hotbar from a standard menu. You would be able to choose the hirelings stats (Str, Dex, Con etc.)and enhancements. Feats and Spells could be standard (the player choosing some for the hotbar as mentioned above).

If possible/practical, the player would be able to choose a dominant AI attack for the hireling. For example some hirelings like to cast sonic blast or implosion or use a crossbow or wield a mace etc.

This would be a gold seal hireling that stays in your inventory (like battlecat does).

Last, provide the ability to name and create a bio for the hireling.