Also Leyline of sanctity with double white ... I don't see the purpose. Maybe in your meta game ?
I would go for more Hydra's like Pulokranos and hydra brood mother
Yes, maybe the leylines doesn't fit well.
Instead, I haven't choose any of the Hydra's with the Mostrosity
X ability, just because I think that
unbound flourishing does not double this effect, because with the first one it become monstrous, and so the second trigger does not resolve.