You can use most parts of my BTCheckpoints mutator as a base. In fact, I believe you only need very small additions to achieve what you want
Since my mutator is open source, you are welcome to do with it whatever you want! Although, if you have some questions or need some help, dont wait to ask me, I'll do my best to support you in your project if you wish
Do you have any experience in UnrealScript btw?
Get the mutator and the source from
here
I would recommend using a seperate mutator for the AntiBoost objective, btw.