I actually spoke with one of the CGL employees (I'll avoid associating myself to him by name) a few years back about writing an "everything designer". I was going to do it for free, my only stipulation is I needed them to be able to timely answer various questions that came up during the design process.
All seemed well, until I sent them a copy of what at the time was my database of equipment, around 2000 rows with over 100 columns each. I already had quite a few questions on things like availability dates and rule inconsistencies. I even saw an internal email from Herb going off because of the amount of issues in the RS products being produced with their amazing amount of errors. All seemed good until I submitted that database, at which point I believe it overwhelmed them a bit and they didn't want to answer questions.
I'd still do it for free (heck, I already am, but right now my motivation is <1% of what it would be if they asked) under the same conditions.
But without getting prompt answers on design issues, well, who in their right mind would want to take that on? It'd go like this:
Step 1. Design
Step 2. code, code, code...
Step 3. question
Step 4. wait... wait.... wait...
Step 5. Try to remember where you were at in code by the time your question got answered
Step 6. code, code, code...
Step 7. Some new ruling or book comes out, requires big code change, all without discussing it first
Step 8. The search for a new developer commences
CGL needs to actually invest themselves into doing such a beast. They need to all understand EVERY rule change, from that point on out, even if just proposed, needs to go through the desk of the programmer. This way they can keep the code "ready" for the imminent changes that WILL be required.
This was HMP's issue, and SSW's flaw. They are hard-coded to a specific way of doing things. Introduce a superheavy mech, or LAM, or "illegal quirks", and all the sudden your entire design goes in the crapper. I've made my stuff modular enough that adding superheavies took me an evening, LAMs will do the same, and there aren't many things that could be added I couldn't implement very quickly compared to most solutions out there. Course, there are more than just mechs too. We have support vehicles, mobile structures, infantry platoons, RPG characters, buildings, etc, etc...
Excel, as awesome as it is, in projects this large end up becoming so difficult to support, that a pen and paper end up being better.