Can brief LTR-ing allow bonus deprec. of 1st home improvements?

[Jacob Radford]

Thanks in advance to this great community. I'm wondering if a brief stint as a MTR can make my primary residence eligible for bonus depreciation of improvements?

BACKGROUND: I'm a high-income professional and my wife is a realtor with REPS. Currently we have a 3-door portfolio of STRs in Gatlinburg and one MTR condo in Nashville. Our family is planning to take a one-year sabbatical from Summer 2024-2025, and we plan to rent our primary residence in Nashville while we're away. That primary residence is a ~4000 sq ft house in a desirable neighborhood, and my wife tells me it would rent for ~$10,000/month to a sizable market of higher-income families looking for an MTR when they first move to town or are completing a home renovation. I'm wondering if we could do a large home improvement (think pool, guest house, addition) in either early 2024 or late 2025 and claim that as a capital expense with bonus depreciation since the property at that point will technically be an MTR investment property just like our several others. I understand that bonus depreciation is phasing out to 60% in 2024 and 40% in 2025, so I would prefer to do this project in early 2024  (and of course get higher rent as well). So my questions are:

1. Will the IRS allow this at all?

2. Does it matter to the IRS if I do it in early 2024 before renters, or late 2025 after renters?

3. How rigidly do I have to keep it within one of the calendar years that I'm renting?