Is there any way, without having to change the original theme, to have more icons on the same row?
Not that I have seen.
Alternatively, is there any suggested theme, same/similar as the original one, but having such a feature?
While there are themes for the 9800, they are all made with buggy software. RIM's Theme Builder is still in Beta for the 9800 and has some bugs. Since all themes are made with this software, they all have the same bugs. I recommend you just bear with it for a little while or purchase a third party launcher program with QuickLaunch or ShortCutMe and assign it to the convenience key.