Good luck with shoulders OP. Generically speaking, they do arthroscopies for rotator cuff and labral tears, replacements for bad arthritis and reverse totals for both RTC tears and arthritis. They won't do both at the same time. You wouldn't be able to survive and that would be inhumane. You would have to convince a friend to come over and feed you, wipe your ass and if lucky hand job every now and again during your recovery... I know Dave Palumbo has had some shoulder totals with maybe one being a reverse and he looks pretty ripped just doing cardio at his age.
My perspective with joint longevity is that if you cannot do a thorough rotator cuff workout/exercises on regular basis then you shouldn't be doing much else as strong flexible RTC muscles protect your shoulder. And if you are void of both flexibility and strength of the RTC muscles and doing still doing heavy movement this allows for more invasive force upon the joint as well at RTC/labrum. Rotator cuff muscle are like the core of the shoulder like our torso is the core for our spine.
Of course keep us posted and again good luck!