Can XeTeX | LuaTeX use MetaFont fonts?

Question

Can XeTeX | LuaTeX use MF fonts invented for TeX ? By default (when fontspec package is not loaded) they load Latin Modern fonts as the following exception from eu1enc.def file shows:

\ProvidesFile{eu1enc.def}
     [2010/05/27 v0.1h Experimental Unicode font encodings]
\DeclareFontEncoding{EU1}{}{} 
\DeclareErrorFont{EU1}{lmr}{m}{n}{10}
\DeclareFontSubstitution{EU1}{lmr}{m}{n}
\g@addto@macro\nfss@catcodes{\@makeother:}

Latin Modern (on my computer with MiKTeX) exists in the form of Open Type (otf) and Postsript (pfb) fonts only. They contain merely Latin script. Wouln't it be better to use, e.g., Linux Libertine fonts (which contain more scripts) as default and error font for XeTeX | LuaTeX? With Linux Libertine LuaTeX | XeTeX would produce reasonable output for many languages (e.g. cyrillic) even without fontspec. This would provide better benchmark point. I mean that minimal example file would be compiled without troubles:

\documentclass{minimal}
\begin{document}
Hello world!
Здравствуй, планета!
\end{document}

At the present state of art, "Здравствуй, планета!" will be lost.

Answer 1

I can't speak for XeTeX, although I am very sure that both LuaTeX and XeTeX can load metafont fonts. So the answer to your question is "yes". But if there is a Type1 or OpenType alternative, I'd always go for that.

LuaTeX loads cmr10 by default, not latin modern. Of course one could change that, but the idea is to get as much portability between the different engines as possible. So if you run a document through PDFTeX and through LuaTeX, both results should be the same.

The user is supposed to use the fonts he or she wants. Computer Modern und thus Latin Modern has the huge advantage to be a) free b) a big set of fonts (italic, monospaced, sans serif,...) and distributed with all ancient TeX systems. If the distributions chose another font as the default font, nothing much will be gained as there is not really much to do more than:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Linux Libertine O}
\begin{document}
Hello world.
\end{document}

While in principle I like your idea, I think it is extremely unlikely to ever happen, so I would not bother to think too much about it.