It is obvious that we can't have a polite debate, or even advocate for a particular side--So I'll stick to the facts and keep observations to a minimum. In closing, my main and only suggestion was, due to the level of modernizations this fellow FAQer was thinking about for his '70--he might also/instead be a good candidate for something like an E30, which could provide more freedom for creativity.
If you track ebay 2002 sales (most of us do) you will find that nice original or well restored examples bring the highest cost. Take that really nice green/white car that was on last week as an example--I'm sure the seller had WAY more in it than the $10,320 selling price.
http://cgi.ebay.com/ebaymotors/One-of-a-kind-1971-BMW-2002-Highly-Modified-NLA-Parts_W0QQitemZ120080813149QQihZ002QQcategoryZ42601QQrdZ1QQcmdZViewItem
Ben