Can MSEgui+fpGUI uses Lazarus packages, like LazOpenGLContex and BGRABitmap?
No you can't use Lazarus components directly in MSEgui or fpGUI projects. Saying that, MSEgui does have its own OpenGL components. fpGUI doesn't yet, simply because I have never been interested in OpenGL (that's until now).
As for BGRABitmap. I believe there is official support for fpGUI now - added by the author of that project. I've never tried BGRABitmap though, my preference is AggPas, because it generates amazing output, sub-pixel rendering and also has a user configurable graphics pipeline (just like "modern OpenGL").
Switching from Lazarus to fpGUI is very easy. Even porting whole components is quite a simple process. The usage is (writing applications and using components) are very similar between the two frameworks. MSEgui has a very different take on things (different, but not always a bad thing). I've also had quite a few developers tell me that the latency in fpGUI is *much* less than in LCL based applications, so sound processing and graphics applications actually run much better in fpGUI.
Basic image-map font (for OpenGL) has many limitations, the better alternative is signed distance font. I have tried to understand how it works, but still never really use it.
My other idea was to do in OpenGL the same as what AggPas does with text and fonts. AggPas extracts the vector information of each glyph, then renders it like all other vectors. Thus you get access to all kinds of transformations and effects (transparency, gradient fills etc), and can render text at any size. I'm pretty confident the same should be possible with OpenGL - if I have a moment I'll give that a try.