To use a scripting language or not to use a scripting language?

[solidstate1991 via Digitalmars-d]

I'm thinking on possibly implementing a scripting language for my 
game engine for general purpose and AI. At one point I was 
thinking on making a scripting language based on D with 
ECMAScript and Prolog/Planner influences.

Basic principles for the planned scripting language:
  - Adding the possibility for logic programming, mainly for 
decision making engines, could be altered on the fly via code on 
the fly
  - Built-in support for fuzzy logic
  - Scripts that run either on step or time basis, intervals can 
be altered by code on the fly
  - Running from a virtual machine either directly from the source 
code or from bytecode
  - Ability to call functions through the virtual machine
  - Portability with certain compromises regarding to the function 
calls
  - And making this available for other projects, also making it 
optional for the engine as it's not crucial

However I was also thinking on why not just put a few helpers 
into the engine's code for scripting and the AI. I already 
planning to create an automated animator for the engine to 
replace sprites if a certain time elapses (uses milliseconds as 
its timebase to make it independent from refresh-rate), I don't 
think some helpers for creating a decision making engine in D 
would be much harder (much easier than creating a new language).