There seems to be about 100 people, give or take, that are very vocal about this issue on this board. Marriott is probably not going to change the terms of the new loyalty program or write special IT code for 100 people. There are probably going to be technical issues in the merging of the programs that will affect thousands of people, and those issues will most likely take priority.
Maybe your best chance is to organize a response after August 1. I wrote into Marriott Rewards on my own behalf. I have enough Marriott nights for LTP, but need points. I actually have enough SPG points, if they were combined with MR points, to put me over the 2 million point mark. So I asked about that. Here was their response.
Thank you for contacting Marriott Rewards.
Unfortunately, there are too many variables which could affect the outcome regarding the upcoming changes. Providing an ambiguous answer could result in misinformation, which would be a disservice to you as a Marriott Rewards member.
We would need to review your account details in August 2018 in order to provide a more specific answer, as we strive to consider every inquiry or concern on an individual basis.
Additional stays and elite nights will affect your combined status in August.
Based on the number of people willing to organize on this board, maybe your best shot is to contact Marriott Rewards individually after the programs combine and ask for special consideration for your personal situation. Just a thought. There could be multiple ways to approach this issue.