I'd love to have auto-capitalize-sentence in the editor.
This is sorely needed for latex/plain text.
Can you please give some example here how it shall look like?
A preview is available on current geanylatex devel to be downlaoded from svn as described on http://frank.uvena.de/en/Geany/geanylatex/
I haven't looked at Frank's work, but just to mention it might also be possible to use the 'Edit->Format->Send Selection to' command with a script to capitalize the current selection.