The Z3100 also has an optional take up reel for about $2k, I believe. You'll get better gamut out of it than a Z6100, but I think the Z3100 is about 1/3 to 1/2 the speed.
If you're serious about durability, then you might consider the eco/light solvents also. We have some customers looking to mass produce for sales to doctors offices and such, so speed and print durability are high on their list. Yet, they still have to look very good (though not excellent). A lot of the eco/solvents out there look horrible from an art standpoint (especially anything with a Xaar print head, like Infinity), but I was extremely impressed with the Mutoh Valuejets and the higher end Mimaki's, the JV5 I think (it was out of our price range). The gamuts are getting better and better with the solvent inks, they last forever and a day indoors w/ decent life outside, and some models like those I mentioned are matching aqueous in resolution. The Mutoh's also have this neat wave print pattern that reduces the effect of misaligned print heads and clogged nozzles, essentially making banding a thing of the past.
You're looking at $15k and up for solvents, I've gathered. The 64" Mutoh runs about $21k, but that includes a take up reel unlike many models.