Depending on how quickly you pick parts and assemble the droid, I think it is possible to finish in 15ish minutes. But that would be pushing it and you’d be rushing through the experience. If that is what you want, then go for it. With my DS6 and DS5, I think the whole process from walking in the depot to walking out was closer to 30 minutes. And I was rushing them. We were late for an ADR and I was frustrated, kept helping them with the assembly more than I should have. Looking back on it I wish I had just relaxed and let them enjoy it more.
I’m not sure about waits for MFSR or SDD at park opening, but SDD waits are usually long all day. MFSR waits can get reasonably short after the initial rush, especially at the end of the day. Same with SDD. A week or so ago at the end of the day, I practically walked on to MFSR and only waited about 30 minutes for SDD, which is more fun at night in my opinion. Toy Story Land at night is beautiful.
Some info that would help getting you better advice would be how large your group is and the date of your trip (high crowds or low crowds expected)?