The help could be in the form of Spirit cultivators, resources, or access to various attack and defensive formations.
Unlike the Big Five Sects, Aksai's Emerald Cove Guild did not have a reliable battle formation that could be used by multiple Spirit cultivators.
As such, Aksai wanted to borrow the Purple River Sect's battle formation technique to create one that could be used exclusively by his own guild.
Basically, Aksai was trying to create a not-so-unique battle formation that was heavily inspired by the Purple River Sect's battle formation. The quickest way to gain a stable formation was to copy it so that it would only look different from the outside.
With Aksai's Neural Link Fabric, it wouldn't be difficult to make his inspired battle formation produce distinct Spirit signatures as well. It would provide the Purple River Sect with plausible deniability and keep the martial alliance a secret for a considerable amount of time.
