how to tag block of apartments with units?

Hello, I would like to tag a group of apartment blocks, which share the same postal address, and which have several units (German: Stiegen). Each unit has a number and is the entrance to the apartments above.

The units are numbered 1 to 8 in this case. The address is usually written like "Hermann Broch-Gasse 1/4".

This is the apartment complex in question:

• Address: Hermann Broch-Gasse 1, Wien / Vienna, Austria
• Way link: http://www.openstreetmap.org/way/90032986
• Geo coordinates link: http://www.openstreetmap.org/#map=19/48.16516/16.30273

What I have done so far:

1. tagged the units with separate "addr:housenumber" and "addr:unit". House number is the same and unit is numbered according to the surveyed units there.

Expected result:

1. A label in Mapnik with something like "1/1" "1/2" "1/3" etc.

Unexpected result:

1. A label in Mapnik with 8 times the label "1" for "housenumber 1".

Ugly work-around:

1. Tag with addr:housenumber="1/1" "1/2 "1/3" etc. and remove the addr:unit, but this is ugly, because in applications like OsmAnd, this shows up as a separate house number, even if it's just a unit. Also, it goes against the purpose of fine-grain tagging.
2. Tag with addr:housenumber="1/1" "1/2" "1/3" etc. and keep addr:unit, but this will create confusion sometime in the future: Maybe Mapnik would later label it with housenumber+unit, which would be "1/1/1", which is clearly wrong.

Proposed solution:

1. Enhance Mapnik with labeling of units, like "1/2", "1/3" or another, country-dependet form.
2. Please also give proposed recommendation for tagging so that I can finish tagging this apartment complex.

Thanks.