No, that's the weakness of optimizing your data store for simplicity and then sticking with the choice for decades after people identify scalability problems. The format you choose for storing email is not a "component".
Also, databasing email doesn't break "everything but MTAs". Commonly used MUAs use IMAP or something web-oriented to talk to the mail store, so they never know about the change. You're asking for an MDA change, so of course the MDA will change -- but not break.