Welcome to Android Forums, pmokover.
I think you can accomplish what you are trying to do, but I will point out that while the Blackberry lags behind other smartphones in many areas, mail and messaging isn't one of them.
First you will have a primary gmail account that the phone is registered too so that the market recognizes you and you have unified access to Google services. You can share one primary gmail account across multiple devices but you only have one primary gmail account per device. If you ever want to change the primary gmail account, you must perform a factory reset to wipe the phone of apps and data.
The gmail app/account is a push mail account. You can set up multiple gmail accounts in that app but only gmail accounts. For other mail like POP or IMAP accounts, you will use the mail app, which polls to retrieve new messages. You can have multiple mail accounts in that app as well, so in essence you have two apps for all your mail.
If you are determined to have only one app for mail, you can poll the gmail accounts from the standard mail accounts and turn off the gmail app notifications. This is counterproductive in my opinion. The other alternative, and one that works well for many, is to have gmail set up to fetch and forward your other accounts, turning them into push services.
Of course there are a plethora of third party mail apps that will provide other functionality as well. Many find
K-9 Mail | AppBrain Android Market to be better than the stock mail app, but it suits me just fine for daily use.