I read your article with interest as I have experimented with collimated illumination of black and white negatives for digitisation also.
Instead of placing the camera facing up into the enlarger, I removed my Durst L 1000 enlarger’s lamp-house and condensers and installed them upside down in their correct relative positions in a custom built copy stand. There are condenser arrangements for 4x5”, 6x6cm and 135 film (24x36mm) which can be adjusted in height for specific lens focal lengths and enlargement factors. The lamp-house can also be adjusted in height. The setup currently uses a Photocrescenta 150W Opal Lamp, of the era.
The Durst instructions do recommend using a replacement point source illumination for greater sharpness and definition and one is currently available on eBay? However, using it requires the condensers to be “surface coated”, I assume to avoid flaring. Also the 12v 100W lamp requires a power supply, and the lamp is probably not replaceable. All this has been too much so I have dropped the idea, my current camera being only 24MP.
And, yes, polarising filters are only required for reflection copy work.