Tweaking the thickness of \triangle inside a \markup?

[Richard Shann]

I am trying to control the thickness of the triangles created by
\triangle command inside markup (because they are a bit thin for chord
symbols on small screens)

\version "2.18.0"
{
a''-\tweak thickness #0.2 ^\markup { \super \triangle ##f}
}

works, but is it possible to put the tweak inside the markup?
I ask because the very nice function

 (sequential-music-to-chord-exceptions ...)

that farms a set of markups for chord symbol definitions does not pick
up the thickness tweak if done like that.

Richard