You could do something like this:
A main company site widgetcompany.com, and then a "company network" type domain with subdomains for each branch of the business. The difference between the two is like comparing microsoft.com to msn.com. Buy the domain names for each company/division in the group, and have them redirect to the real site which is a subdomain under the "network" domain. So you get,
- widgetcompany.com (Group marketing and company info, financial info, annual reports, etc.)
- mywidget.com (umbrella site for each division)
- widgetdesign.mywidget.com (individual sites for each division)
Keep a common look-and-feel accross the subdomains, with navigation up to the mywidget.com umbrella site (no direct cross-linking between subdomains - send then always via the mother ship!) so the customer can see what else the company does.
As I said, that's just an idea of how you can approach it!