Hi Kris, this message may be too late but natively in NetSuite there are two main options if Suitebilling doesn’t seem like a fit.
1. ZoneBilling - I work for them for full transparency.
2. 360 Cloud solutions.
You can obviously look at 3rd party solutions like Recurly, maxio, Zuora, SFDC revenue cloud. But you’ll need to integrate to NetSuite and that can either be fairly easy or really difficult depending on requirements around reporting and rev rec. Also those can be expensive and typically take a % of revenue which is typically unfavorable.