individual tie directions in chords

[plutek]

in the following:

\score {
\notes \relative c' {
<f g c>~<f g c>
}
\paper { raggedright = ##t}
}

it seems clear to me that the tie between g's should go up, to avoid
colliding with the tie between f's. unfortunately, that does not follow
the rule of curving away from staff center.

i have not been able to find a way of controlling tie DIRECTION for
individual notes in a chord. i suppose the method of placing the tie
engraver at thread level (shown in regression/tie-chord-partial.ly) would
work, but in the context of a succession of chords, where only one needs
this treatment, isn't it difficult to switch between that and the regular
use of the tie engraver?

is there no simpler way to do this?

-p