Leo,
I agree in principal but I do not believe that attaching cutomised information should be done via GDL script and variables (and I appreciate that your proposed workflow is based on utilising existing resources).
Edited: in fact we do have this implemented for lib parts (only) based on subtype templates (see Parameters for Listing in the parameter list of any standard GS lib). This is just 'hangover stuff' originated in a long dead GS's Property Management Software (I have forgotten its name already).
All of this should be done by independent 'tags' sandboxed from the lib part GDL code itself. This way any changes to a lib part's code (eg. upgrades, debugging, version migrating) or actual replacement of the lib part itself (replacing eg Chair1 by Chair2 would not necessarily delete all information already attached to Chair1) would not have any impact to attached customised information. Also, tags would allow attaching customised information for non-GDL elements too.
And surprise, surprise it is already there however it is not 'wired' properly. If you went to Scheme Settings/Available Parameters/General you would find 'Custom Text #' variables (AC11 has 3 only but AC12 has already 10 of them). These are in fact customisable tags attached internally to each particular AC element.
Flaws:
1. they are not visible in the Default Settings dialog (the best place for them should be the Listing and Labeling tab).
2. they are not visible in Element Information palette
3. they are not visible to associative labels
4. They can not be renamed so we could see what is what in eg Default Settings dialog.
5. Point no.4 leads inevitably into another shortcoming and that is - each individual AC element type (slab, window, door, beam, column... etc) has to have its own set of tags (and to be fair may be 10 per each set would be enough). To explain what I mean here is the example: if we renamed let's say 'Custom Text 1' to 'Type of glazing' (Windows/Doors) with current system it would be shown as 'Type of Glazing' tag for all AC elements (eg a wall) which is not desirable. Therefore we need to have different sets of tags per each
element type
(note!: I do not mean an element instance here.)
6. and of cause tags should be connected (import/export-wise) to some common database types (Access or FileMaker). However I do not believe that Excel is a proper tool for it as it does not handle 'records' as such. eg each individual database item has to have its unique 'key' (or ID as you already suggested) and that is not possible to maintain automatically in Excel (imagine a big list of items - if somebody moved a field it would be a mess and definitely a dangerous practice too).
Anyway, GS has provided yet another alternative (which is obsolete as hell) - property objects but that is another cup of tea I do not wish to go to... I just simply do not want to spoil my day cursing this 'piece of work'
::rk