Darius,
I'm going to pick a nit with one thing you said:
Smalltalk's strength is that it's easy to change, but that may be a weakness here. Often in professional games, you don't want the games easy to change by the players because the temptation to cheat is too large.
When I was a kid--and the bar was MUCH lower on games, as in, a single person could code a viable commercial game in a month--I used to enter games from listings, and changing them was an excellent way to learn this particular skill:
Also, quality of game play...is a skill that takes years to learnby practice and failure and lots of testing.
Nothing gives you that skill faster than being able to tweak the rules of a game.
Hell, even some of the commercial games we bought back in those days came as Basic programs that you could stop and hack. And you'd learn pretty quickly which rules were important and why.
That's afield of the commercial issues, of course, though it should probably be pointed out that modding is at least one source of game programming talent these days.
===Blake===