The keys to this are rules, rules, rules. Clearly you can't keep the Flash centralized when the rest of your organization is decentralized. They won't stand for it, and you probably don't have the resources to manage it anyway.
Here's one approach to take:
- Simple animations can be allowed sitewide - limits should be set on what counts as "simple", but they can do what they like
- Applications and complicated pieces must go through an approval process at the "corporate" level - no exceptions. This keeps the overenthusiastic from hogging bandwidth, creating problems, etc.
- Establish who's doing the work, and make that clear to the less technically savvy. You don't want people coming to you to build stuff you know nothing about and want nothing to do with. If someone builds cool functionality, it has to be their job to maintain it (not that you can't "liberate" really cool tools and apply them in other places if it's appropriate)
- In that vein, I'd suggest part of the project planning include a maintenance section - i.e., what happens if your brilliant flash programmer leaves? Who's going to maintain the site/piece/application? I'd include a requirement for thorough documentation for the flash piece, and that your dept get a copy so someone keeps track of what's been done.
I'm sure there's other things to think about, but this is what occurs to me now.
I think you can easily defend the decision to start with the Flash at the corporate level - it's a controlled experiment to understand the implications of adding the functionality to your site. If you get your rules in place before you open the gates to the Ravenous Ostrogoths, explain them clearly, and insist on compliance. As long as the rules are in place before you start, and apply equally to everyone, they can grumble all they want.