I am planning to build a vertical tack locker for my garage. Security is an issue–my saddle is worth more than my little trailer.
So anyway, what I want in my locker, and I think your clients would love, is a pull out or swing out saddle rack. I’ve been looking at cabinet hardware catalogues for heavy duty/industrial drawer sliders, or trying to come up with something I can rig together. It’s not worth an extra $200 to me, but maybe $75.
As far as finishes go, I’m just going to use plywood/veneer. If I were you, I would have a couple levels of finishes–one for the utilitarian like myself, and one for the fancy barn level.
With a locker (vs. my tack box) ventilation will be important to me, but also keeping dust off (we use saws in the garage sometimes). Rather conflicting goals, I know.