You know, it strikes me as tho the genitive plural is very adjective-like, and since it was/is traditionally in form the same as the common singular, it's a bit like how in English you wouldn't make an adjective agree in number with the noun (usually), for example, 'fluffy puppies' not *'fluffies puppies).

But what I want to know is how (if possible) to separate 'bale gathering' and 'the gathering of (the) bales' (a'bailiú na mburla(í)) ? Maybe they'r not even two senses and I'm just splicing here

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__̴ı̴̴̡̡̡ ̡͌l̡̡̡ ̡͌l̡*̡̡ ̴̡ı̴̴̡ ̡̡͡|̲̲̲͡͡͡ ̲▫̲͡ ̲̲̲͡͡π̲̲͡͡ ̲̲͡▫̲̲͡͡ ̲|̡̡̡ ̡ ̴̡ı̴̡̡ ̡͌l̡̡̡̡.___

I think the nouns that end with -a in the singular would always have an -aí in the genitive plural:
burla -> na burlaí, na mburlaí

A' bailiú na mburlaí
a' bailiú burlaí

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne