Well, I think it's better to make a new word not have an irregular pronunciation, where possible. 
Also, one can check how people are using the word currently. A simple unscientific method is to use an Internet search engine. Google finds about 6850 instances of "moding", including "MODing" and a different gaming term, which has to do with role-playing (see  
THIS LINK ). 
Google finds about 235,000 cases of "modding", however.
PvK
 
 
[ December 23, 2002, 03:00: Message edited by: PvK ]