If I could Make a suggestion?
TS12 adds great functionality for dealing with missing assets.... IF you found someone willing to work on your routes for you, to replace what was missing, would you make them available?
The other thing I can suggest is make them available anyway, publicly, AS IS, just put a disclaimer to the effect of "Warning: Many dependencies are missing. Replace or Delete at your discretion. Author holds no responsibility for the completeness of downloaded content" This could be expounded on depending on specifics, but that should absolve you of personally having to deal with it. I'm sure there are people here that, would at very least, on their own, compile a list of whats missing and whats still available. Be a great organizational task for somebody thats really bored....
And btw, Don't worry about the Total number of Assets.... As of the radio show this morning, my CM knows of ~350K, I personally have over 100K Locally, and the average serious Trainz player has over 50K. People will adapt to what they want to do.
Finally I'd suggest to not let the missing Payware worry you too much. Just because XYZ Locomotive is Copyrighted, doesn't mean you can't distribute Things that *Reference* that locomotive, you just can't include any part of that locomotive. Same with trees, Buildings, etc etc. Check out the MBC2012 Route that uses Payware Pofig(? Might have been JVC, can't remember, I just know to buy them costs $100) as an example. The route is free though.
Hope this helps
Falcus