Yes, that's a good question. My worthless guess is they might skip starts in the AAA rotation to save innings as one measure of "saving" innings for eventual call ups. They've already got all but 2 Mondays off this season, so there's one day off per week there. Maybe they go with a combination of RP every once in a while to skip or push back starts throughout the season.
They might also push back starts for rainouts. Postponements that are made up are done so as 7 inning doubleheaders. So, when the opportunity allows, they might go with the SP in the first game and just bring in RP for the rest of the day. Maybe they start the second game of the doubleheader with a multiple inning RP or even piggyback a game with 2 multiple innings RPs. Something along the lines of two pitchers going 6 IP and 1 IP in game one and three pitchers going 3, 3, and 1 in the second. That's an overly simplistic example, and the opportunity might not present itself all that often. However, the pre Memorial Day weather does present itself to be more likely for Mother Nature to assist with this. So perhaps they can bank a few innings early on in the season.
I think the key to maximizing the availability of SP depth is going to be in saving some of those innings in AAA for later use in MLB. Its good to have the depth on a piece of paper. But gating that availability through the health issues and slumps that the Tigers (or any team) are likely to encounter throughout the season are going to have to be plotted out with guesstimation to some degree.