MMR is a CMP label for their type of sanctioned matches. I know this forum is for CMP competitions. But there are other AR-type Service Rifle/other label competitive matches, and many more than those held by CMP. There is no need to give up on the hobby.
If you have any NRA-sponsored High Power matches within your area of access, and check the 2018 NRA High Power Rule book you'll see that their Service Rifle category nearly duplicates the 2018 CMP MMR configuration specs, as they did in prior years, but without any specified weight.
I haven't seen the 2019 NRA High Power Rules yet (May-ish) but if that pattern holds its likely you're good-to-go for a NRA-sanctioned match with a CMP MMR configured AR. You just won't have to deal with the 7.5 lb. threshold, if the NRA continues not to specify a weight limit.
Look in the Coming Events section of Shooting Sports USA (monthly-on-line only) for any scheduled matches within the area you're willing to travel to.
https://www.ssusa.org/coming-events/ or in the SSUSA e-magazine.
http://www.nxtbook.com/nxtbooks/nra/ssusa_201901/
Here's the Jan 2019 schedule.
https://www.ssusa.org/media/1539923/jan_2019_ce.pdf Check regularly for updates since its early.
Here's MI contact. MICHIGAN, Utica: 200 YD, May 1-Oct. 31; L. Fey, 21046 Lantz St., Clinton Township, MI 48035;
lfrey1816@comcast.net
BTW, an NRA "match" AR has equivalent specs as the CMP " Service Rifle".
https://rulebooks.nra.org/documents/...R/hpr-book.pdf