Looking for experienced SketchUp Ruby developer for lightweight data-extractor extension

So you can also see that there are others interested in some of these aspects you mention.

With regard to time / scheduling see this topic thread:

SketchUp 4D Timeliner Concept – Looking for Ruby Development Support - Developers / Ruby API - SketchUp Community which has links to 2 existing extensions.

With regard to Material Requirements Planning (MRP) look at what OpenCutList has achieved so far:

Approvals / Inspections would vary by jurisdiction. I could see a Boolean field, perhaps a date and a link to external documents being helpful. But a quick search shows nothing in the Trimble Extension Warehouse.

Re Cost / Procurement, there have been quite a few attampts: