If you'll actually use it, then no I don't think it's overkill. My daughter gave us a towel warmer several years ago as a gift and we put it in our masterbath because we didn't want to offend our daughter by not using the gift. Our masterbath is quite a bit larger then the bath you're talking about so it wasn't overkill. But we've never used it. Never. We plugged it in when we first installed it and draped a towel over it, but it really didn't substantially warm the towel enough to make a difference. We're remodeling the masterbath and the towel warmer is not making it back into the bathroom.

Do towel warmers help prevent musty smelling towels? I had no idea. I just assumed they were a luxury for having warm towels when you come out of the shower or bath. Do you have a ventilation fan? I think that can make a big difference in terms of musty towels and mildew in the shower.

I'm in Seattle. I have Runtal towel warmers in all of my bathrooms. Aside from the delightful luxury of having a warm towel when you step out of a tub or shower, you'll never have musty smelling towels again. In our climate, I think a towel warmer is almost a necessity. I use it the year-round, although I do lower the temperature setting in the warmer months.

My towel warmers are on automatic timer and temperature controllers. They come on in the morning automatically, then turn off during the hours when they're not needed (I can override the setting if my usual schedule isn't adhered to). They are simply wonderful. It's amazing how quickly you get spoiled. When I'm away and have to dry off with an unwarmed towel, I really miss it.

Mine are the Runtal electric Neptune models. I highly recommend them.

Here is a link that might be useful: Runtal Towel Warmer/Radiators

Try washing towels with borax. It really helps with the musty smell!

I'm so darn hot by the time I get out of my tub that a warm towel is the last thing I want. I DO however miss my warm toilet seat when I away from home! :)
Monica

I live in south Florida and I LOVE my towel warmer.

I'm in the Northwest. I have a 5x10 master bath with a forced air vent and an exhaust fan, and I don't get musty towels.

I'm going to try a towel warmer on the remodel anyway.

I live in the south (think humid!) and love our towel warmer. Not so much for the warming as for the drying. I do "linen" laundry once a week and have no problem with a musty smell any more. Also nice to have a dry washcloth for my nightly face washing!
We bought the freestanding double layer Vauxhall by Warmrails for our masterbath. Keep it on a timer during the summer months so as not to add to the heat of the room.
I also use an old junk towel to dry off the shower after squeeging and so that goes on the back rack out of sight after use. I only have to wash it with the weekly linen laundry and not have a wet junk towel to deal with every day.