In Cnósach Focal ó Bhaile Bhúirne p84, under deagh-lán (dea-lán, capacious) there is this: níosa mhó slí bheth istig ann ná mar fhéachfadh sé chun a bheth.

I can understand it, but I hadn't expected "chun" in there. I had expected mar fhéachfadh sé a bheadh. What do you think? Does it make sense to you?

The first thing I thought was "a" as possessive: "chun a bheth"/"chun a bheadh" > "towards its being"(?) but I'm curious as to what others might think.

I think "a bheith" means "being it".

Hmm, yeah. So, why would "chun" proceed that? It seems like the writer wants to show intention . . .

Kind of like "more space in it than it would looks towards there being".

That makes sense.

It's basically the verbal noun version of the conditional clause you gave as an alternative. Oratio obliqua style verbs (e.g. ordaigh*, síl) used to prefer the verbal noun clause over a typical verbal one, but even in the past it was rare in a case like this where there is no noun as an object or a following progressive.

So indeed:
more room inside than it would seem that there would be.

*"D'ordaigh sé iad a dh'fhanacht anso" for example. There's a Kerry/Cork split on fanacht/fanúint.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal