\DeclareEmphSequence

[xworld21]

LaTeX >= 2020-02-02 supports changing the typestting of \emph{} via \DeclareEmphSequence. It's tricky to replicate it in LaTeXML, because the behaviour of emph is hardcoded in (at least) two places:

LaTeXML/lib/LaTeXML/Common/Font.pm

Lines 800 to 802 in 3812528

	if ($options{emph}) {
	$shape = ($shape eq 'italic' ? 'upright' : 'italic');
	$flags |= $FLAG_EMPH; }

LaTeXML/lib/LaTeXML/Engine/LaTeX.pool.ltxml

Lines 476 to 478 in 3812528

	beforeDigest => sub {
	DefMacroI('\f@shape', undef,
	(ToString(Tokens(Expand(T_CS('\f@shape')))) eq 'it' ? 'n' : 'it')); });

I guess this will be automatically resolved by reading latex.ltx raw, though.