I was a civilian in the Police up until 6 December 2015 when I took early medical retirement. It was an easy decision for me as I was 62. It all worked out very well and I received tremendous support at work and I was treated with compassion.
It seems that your partner has taken the correct initial steps by speaking to the Federation and OH. I know from colleagues that the full officer shift pattern is demanding and it is difficult to build in breaks during the shifts. I do not know, of course, what OH may have recommended, if anything.
Even though I had a desk job I found that fatigue was a huge issue. Even when I reduced my weekly hours to 20 I was a zombie after my shift. I also suffered from bladder urge incontinence, a common symptom of MS, and had to be near to a loo.
How you proceed depends on your partner’s symptoms and which type of MS has been diagnosed. If it is RRMS then the new thinking is to start disease modifying treatment immediately, and you can discuss this with your MS nurse. I would suggest speaking to the MS nurse for most matters, as you are only likely to see a neurologist about once a year. It may differ in your area.
Your partner may be able to carry on with a full shift pattern for some time, depending on the nature of the position, and your partner’s condition. I can sense from your post that this may not be the case. If so, you will both need to discuss a realistic contingency plan together, and then involve Federation at every step. Make sure that a rep attends every meeting with management and HR.
I cannot offer anything more specific without knowing more and, of course, I am not a neurologist. There are many leaflets in pdf form available on the MS Society website which provide valuable information on all aspects of MS.
If there is anything I can do I will do my best to help.
Best wishes and welcome to our club.