Interesting project!

You surely know of the ISO LADM standard. Now an OGC conceptual standard, LandInfra, is available, too. A use case for 'Forming strata title / condominium' is available at http://docs.opengeospatial.org/is/15-111r1/15-111r1.html#236 and the concepts at http://docs.opengeospatial.org/is/15-111r1/15-111r1.html#204

I am curious to see the role you attribute to standards.

As for condominium recording Denmark, in 2012 it was decided that 'The Cadastre will have to be expanded to include other types of real property, so that land parcels, individually owned apartments [= condominiums], and buildings on leased land are identified and recorded uniformly in future.'  https://www.digst.dk/Servicemenu/English/Digitisation/Basic-Data

'The Basic Data Programme has been delayed by one year and completion is now expected in mid-2018'  https://www.digst.dk/Servicemenu/English/News/The-Basic-Data-Programme-to-be-replanned.aspx

Good luck!

Erik (Stubkjær)