Try this mach1.met. Just copy it it your game folder. Don't forget to backup the original file.
Play only new skirmish maps with:
default starting resources low starting tech-level fixed positionEvery skirmish map default BMUs is 50k. Low tech-level means low for you and medium for the AI. Fixed position makes the AI always ally with each other. Constructors and technicians are faster and better.
If you want any other enhancements just follow Judas modding guide. It's simple and can let you adjust the skirmish levels to be quite challanging :)