Hi--
I figured out a good way to scan fiche several years ago. The key is to not use a flatbed scanner. The glass on your flatbed that sits between the light and the microfiche distorts the scan an makes it very blurry, in a way that can't be fixed by editing.
I bought a slide scanner, and had some custom glass cut as a holder. I cut the cards into strips, and I tape them onto the glass along the edges with rubylith tape. This works better because I tape the fiche to the bottom of the glass, not the top, so the light captures the fiche image without the glass distortion. It's very time consuming (sometimes 90m to scan a full 68-page book, and another 60m or so to edit), but I've been generally happy with the results. Especially on books that might otherwise be thousands of dollars to buy otherwise. I've done a few that have been posted here on DCM, although most have been replaced with paper by now. I think Green Giant Comics is one that's still a fiche scan here.
Happy to post photos of my gear setup if anyone's interested.
Feel free to PM me if you'd like some help or advice with your scanning project!