The sum of two irrationals might not be irrational so we can't use that; Also $\mathbb N$ is not a group so there's no obvious way to define a group structure in it seen as $\mathbb N^{\mathbb N}$ either. This answer gives some necessary conditions for a topological space to be possible to turn into a topological group. The Baire space clearly satisfies 1,4 and 5; intuitively i think it also satisfies 2 but i'm not sure how to prove it, and i have no idea for 3.
Is there a topological group structure on the Baire Space?