If you with to use slide then let me suggest Astia 100F for this kind of work, it has the best highlight-shadow range /tolerance that I've witnessed in a slide film.
Will it be around long? Well I have a stockpile in my freezer in all formats...
I would also consider a neg film like fuji 160s. Really depends on your lighting conditions, of course, but if you routinely see a lot of contrast and mixed colour balance then I'd just go with a neg film. These will also be around much longer than slide, in my (unhappy) opinion.
If I had to do this purely digitally then I'd just stitch smaller-format digital files. The software has gotten very good now.