Interesting exercise, including how it plays into the trade deadline.
Over the last couple years, we've noted how the Twins have started the season with six starting pitchers with at least some experience, recognizing that it is almost a certainty that someone will be hurt. That meant sliding Ober into the rotation early last year and Varland this year (replacing DeSclafini). That's been a good plan.
Similarly, I've observed that last year and this year, they began with about 16 "legitimate" hitters. By "legitimate," I mean with some level of MLB experience. They are reluctant to have a true rookie above about No. 15 on their roster. I think that's been a good plan. The presence of Margot and Farmer, for example, meant they weren't forced to keep a Wallner and Julien on the MLB roster when they struggled. I think shooting for 16 hitters is a good plan as well.
With that in mind, I don't think there's enough time (barring injury) to get Severino or Rodriguez enough at bats to be above Nos. 15 and 16 on the list, so I've struck them from your list of 13. Even if they get a few at bats this year, I don't think they would count on them for an Opening Day spot, even if it's because that means they don't want to see someone with no experience (Kiersey/Prato/Helman, etc.) in the 15/16 slots.
That leaves 11 on your list. I agree with your implied assumption that Farmer, Kepler, Santana and Margot won't be back.
If we slot Severino and Rodriguez at Nos. 15 and 16, that means spots 12-14 are left. In that context, I think there is a place for Julien, if he continues to hit and gets at least some time back for the Twins.
I agree that Kirilloff is a non-tender candidate. Either way, there is still one or two roster spots open. To that end, good as this overall list looks, I think there will still be at least one Farmer/MAT/Solano/Margot-type "veteran presence" added to the roster.
(Note: I'm not saying this is the way they should do it -- I'm just thinking this is the way they will do it.)