Site architecture revamp or Mod_rewrite for crawlability?

Which to do on a large site?

[jornada11]

With a large, database driven site where the product pricing changes often, does it make sense to try to change architecture (folder names, URL structure) or should I pursue the Mod_rewrite route? It just seems like I can get these unindexed pages in so much quicker with the latter, but I am also concerned about the "haste makes waste" component?

I know there is this big "build it right" movement, but in this case it would be a HUGE (read REALLY, REALLY HUGE) task to coordinate all the different departments, get buy-in, etc. Any thoughts or experiences with this you can share? What are the implications of going one route over the other?

I have control over all of the other on page factors (titles, headers, content)...there are just a ton of variables in this custom built backend that I don't think I will ever get approval to completely change how the URLs are built.

Thanks in advance for you insight.