I would appreciate you advice on how to incorporate parameters into SEO Friendly URLs

We have decided to have the "techie" parameters first, followed by the "SEO Slug"

\product\ABC123\fly-your-own-helicopter

much like S.O. - if the SEO Slug changes, or is truncated, or missing, we still have the Product and ABC123 parameters; various articles say that having such extra data doesn't harm SEO ranking.

We need to have additional parameters; we could use "-" to separate parameters as it makes them look similar to the SEO Slug, or we could/should use something else?

\product\ABC123-BOYTOY-2\boys\toys\fly-your-own-helicopter

This is product=ABC123, in Category=BOYTOY and Page=2.

We also want to keep the hierarchy as flat as possible, and thus I think:

\product-ABC123-BOYTOY-2\boys\toys\fly-your-own-helicopter

would be better - one level less.

We have a number of "zones", e.g.

\product-ABC123\seo-slug-for-product
\category-BOYTOY\seo-slug-for-category
\article-54321\terms-and-conditions

it would help us a lot if we could just user our 5 digit Page ID number instead, so these would become

\12345-ABC123\seo-slug-for-product
\23456-BOYTOY\seo-slug-for-category
\54321\terms-and-conditions

(Products & Categories have a number of different Page IDs for different templates, this style would take us straight to the right one)

I would appreciate your insight into what parameter separators to use, and if the leading techi-data is going work well for us.

In case relevant:

Classic ASP application on IIS7 + MSSQL2008 Product & Category codes contain A-Z, 0-9, "_" only.