Workflow wise, the multicam (or any router) would be ideally suited for sheet stock. We do cut roll stock on our router, but with our setup it's limited to 4 x 8 areas.
To expand, cut your sticky back roll stock on a plotter. Cut your boards on a router. A full loaded OPOS plotter from Summa is under 9k. You could buy one of those, a router and another flatbed for the $ of a zund.
The major bump to your biz with a true router over the zund would be the chance to open up other cutting projects that the zund cant handle. Sure you may not plan to do 3d signs, but your zund isnt gonna cut printed aluminum very well if at all.
Historically, the zund would be a better choice if you print paper based boards (foamcore and cardstock) and need to knife cut, but even multicam now has a knife tool. If you plan to do a lot of foamcore or cardstock, you'll need a knife cutter.
Only other thing the zund offers is scoring which only really matters for POP work if printing B or C flute.
Also, the zund router head is a wimpy setup, the true router will cut anything. And (my opinion) the belt makes cutting semi-rigid panels like ACP really tough to get consistent results. As the belt deflects away from your toolhead, so does your material, and you get inconsistent cuts.
Of course the zund has its upsides. Those happen to only be about 10% of my particular shops workflow. Would I like to have one? Sure. Would it make some jobs easier, yes. But I'd add another flatbed for the same $ first.
Bottom line, there are only 3 things we can't do without the zund: 1. Cut foamcore shapes without post cleanup. 2. Cut .050 cardstock cleanly. 3. Score a or b flute corrugated cardboard.