^^^ For what it's worth, in the Jaeger interview, he says:
It wound up being almost as big as the Enterprise-E – the E is longer, but the saucer section is almost the same size.
So yes, it is entirely possible that it was supposed to be much larger than what was eventually built, and able to support launch tubes of that size.
As for the lost files, I believe that was for the Norway class. Those files were apparently corrupted and unrecoverable. The Akira model, however, went on to be used quite frequently in DS9 during the Dominion War long after the events in First Contact and I think the Steamrunner could also be seen occasionally in the background as well.