Need more details. Your ROM version may clash with mine and if it does that would explain the FC's.
Mine is March 15 4.4.2 CM11.0. If yours is significantly newer, you may have issues with internal compatibility.
Post a just-after-boot logcat to pastebin.com and I'll look at it but can't guarantee I can really give you more help with it than maybe figuring out just why it crashes.
My builds started bootlooping after March 15, so something went different in the internals after that date that really messed things up for me. All system apps FC at boot and respawn.
The source code changes I made have been absorbed by Team-Hydra and LiquidSmooth at least, though I haven't seen them filter upstream to CM. If you can get a dev to build your ROM with one of those repos frameworks_opt_telephony instead of CM's frameworks_opt_telephony it may fix your MMS.