[Mr Bill]

I think our enlargers are built the wrong way round!

They should have the light source, negative and lens at the bottom, projecting upwards onto a piece of ground glass...

This has actually been the standard setup for commercial printers (ie. package printers) for MANY years. A ground glass is used to focus and align all of the lens decks during initial setup. More familiar to the general public were film-based mini-lab printers; you've probably seen the operator sitting at a desk-like workstation to handle the negatives. Above is the lens tower and the paper transport system.

These systems have their own difficulties, one of which is the tendency for paper dust to fall out of the lens tower, onto the negative stage.