tanru
are frequently adequate, but I think we pretty much all agree that they
aren't a "solution", they're a way of getting things across when it's
obvious what you mean.
But
the semantics of tanru fits the task very well. Seltau selects a subclass
in a broad class of relations that can be expressed by tertau. And that is just what we need. The only drawback is that it is undefined, which subclass is selected. :D
ko'e gidva se sinma ko'a
What one would think it can mean, besides the intended meaning? In a typical situation the listener already knows that {ko'e gidva}.
That {tai lo'e nu} construct is interesting, but it seems
to be more like a selbri relative clause (which is what I proposed on
IRC) than a tag construct. ({tai} in general is like this, which is why
I've never particularly liked it.)
{tai} is just a shorthand. We can expand it further:
lo nu mi nelci do ku fasnu gi'e simsa lo'e nu zu'i nelci lo pendo be ri kei lo ka tarmi ce'u