Welcome to the forum @nethead. I have only ever used a 0.4mm nozzle in a printer. I think the main body will be fine with a larger nozzle, and the base certainly should be. The optics modules and the condenser have some thin walls and thin gaps that may not work properly with a big nozzle.
There was someone who planned to print a microscope in ABS, 3D printing material - Request Help, they did not report whether it worked. As I suggested in that thread, printing the z-actuator from the upright version will be a relatively small part that should tell you whether the material will work.
For which version of the microscope to build, your thread title says you are planning dark field of blood films. There is not a well-developed dark field illumination system. There is an LED array system that was developed on the Delta stage to allow controlled illumination aperture. I cannot find it just now, it would fit either the Delta or teh Microscope bodies. Bright field blood film imaging works well using either the Openflexure Microscope or the Openflexure Deltastage with the high resolution optics version and a 100x RMS microscope objective (oil immersion). There are some blood film images on the Openflexure web site. The Microscope (version 7.0.0-beta) is probably the best basis for what you want, rather than the Delta stage.