The font list could be too long, I don’t think most people will need so many.
I suggest: use character to access all font and by default show only liber fonts and place a pop-up dialog tell the user how to use other font.
Default is the POWER!
The font list is pulled from the operating system. Are you are suggesting obtaining this list from the document XML schema? I am not sure this would be desirable until font embedding comes about (and that has significant legal / distribution issues from what I understand). This would also be a fairly distinct UX departure from how office (and other) software in general behaves.
Put Operating System coverage aside, there are very few documents used more than 4 fonts. 12 font candidates are enough for me.
I understand what you are saying, but the reality is that LO is not for one person or task, it is a general purpose product designed to be adaptable to a wide variety of tasks. Like you, I rarely use more than a small selection of fonts, although my selection does vary from document to document.
It is better to start a user survey/vote or opinion website. The user behaviour vary and depend on situation; but like Microsoft did in Office 2003, it auto-hide menu entries, and one click will unveil all.
Check the answers here.
PS. I think there is a bug in Win7 that shows also hidden fonts in the list. If something is hidden it should not show up.
I got an idea what @jiero might like to have.
In MS WORD (most likely in all other MSO applications in the same way) font roll-down menu shows all fonts used in an opern document on top of all fonts. This is indeed a convenient functionality because it shows all fonts used on top and all fonts below in their normal order.
@jiero - It would be good if you please file an enhancement request and post the request/bug number here. Should it be possible please add a screen shot of MS Word and Writer; this would make your idea very clear.