As I understand your goals, you're looking for optics that are:
- suitable for stack-and-stitch
- reproducible (hence using only parts that are currently being manufactured)
- high quality
- long working distance
- simple and robust enough for use in schools.
Those Mitutoyo objectives you link to are certainly reproducible and high quality. But they're listed at over $1000 apiece and it's not clear how far you can push the magnification & coverage. Edmund Optics (for example) also offers numerous other telecentric lenses covering a range of magnifications and sensor formats, but they are even more expensive than the Mitutoyo objectives.
On the other hand, the level of telecentricity provided by these lenses is probably overkill for your work. They are designed for non-contact gauging applications where it's important to make an accurate measurement even when the subject is noticeably out of focus. For your work, what's needed is less stringent: the change in scale with distance must be negligible only within the range of DOF that the stacking software can discriminate reliably.
So I'm pretty sure you're going to have to assemble your own optics, using the tradeoffs that make most sense for your applications. I'll talk with you offline about this. There are too many issues to discuss efficiently in the forum.