I believe the reason he is wanting to use FPSC for prototyping is to prevent him from having to do any real in-depth work (like modding) to get a simple idea into a form for presenting, before moving into any true development of the idea.
It sounds like you're wanting to use thirdperson and some form of RPG elements.
Fenix Mod may or may not be your best bet here. It's worth a shot, though, since it is free. It has a very basic third person support, and has a bit of (outdated) RPG Mod contained within.
Project Blue would be able to cater to whatever you needed, though. Third Person is easily implemented (minus camera collision, which requires far too much setting up to be worthwhile), it has a very in-depth variable system which can be used for RPG elements, it is capable of creating an inventory system (further RPG stuff), and has support for a wide range of shaders (including full screen shaders, such as Bloom and Motion Blur).
Being the one who was Project Blue's main developer for 90% of its life, I can say that modding would not be your best approach here. It takes far too long just to pop out a simple prototype. You would be better off making it from scratch and demonstrating that instead. If your goal is to compile a simple prototype to demonstrate an idea, then you won't be going for absolute perfection. Use one of the Mods and put your idea together. Prototypes are not known for their bug-free attitude and only work well enough for the person who made it to demonstrate an idea without problems. If you are aware of the problems present, then prototyping will not be an issue here at all. 99% of problems can be easily avoided by someone who is aware of them, so they will not show up during a demonstration.
The one and only,
