Tenant wants to modify bathroom...thoughts?

[Slade Harrison]

Little backstory: Rental is a 1300 sq/ft SFH in a great neighborhood in Northwest Florida. House used to be my primary before moving into a bigger house. Been renting to this couple for the past 3 years. They pay via direct deposit, never been late and take great care of the house. They are older (late 60's), retired military.

I was at the property this past weekend spring cleaning, pressure washing, trimming trees, etc... because I self manage both of my rental properties. The husband comes outside to shoot the breeze and I ask about the house, if they are having any issues, he says no but wanted to ask me about swapping the shower/tub in the guest bathroom to one of those walk-in bathtubs...He said his wife has trouble lifting her legs into the shower as it is and that they would pay for the tub and install. I told him to let me think about it and I'd get back with him soon.

I just worry that if I ever decide to sell the house that a walk-in tub would negatively affect the re-sell value, especially given that this is essentially a starter type home...My initial reaction is no, but then I think that if they want to make this change and pay for the modification, they have no intention of leaving and I would have a very long term, dependable tenant.

Could I stipulate that they can change it out but if they decide to leave they have to swap it out for a one piece shower/tub combo that I originally had? What if I decide to not renew there lease and want to sell the house? I would feel obligated to reimburse them...

Thanks in advance for any advice BP community!