I've never seen a Vim emulator implement this correctly, but it's something I use a lot in Vim. Basically CTRL-O while in insert mode will jump back to normal mode for a single command and once completed will automatically go back into insert mode.
The way the project is engineered this might be a little bit tough to implement. That's a useful feature and I will look into seeing if it's not too tough to add. I know Shu want's to keep the features that are in right now and work toward a 1.0 release that is mainly bugfixes so this might not hit release1.0 but it may hit an unstable feature branch.
Shoud work in refactoring branch now.
(Close when released)