Can I get an opinion on Extending Spark: Custom Tables, DB driven Gateways, etc.

Instead of Users & Teams; I need to have

Users -><- Members:Memberships -><-Orgs

Each Membership of an Org can theoretically have a unique payment id / cards; vs attaching it to user record.

Orgs haveMany Memberships / Members; Orgs haveMany Invoices (one off transactions)

My other need is to load db driven elements for plans, payment gateways for Org, etc.

... So, the $20,000 question:

Would it be advisable to try to hack apart spark and customize Invites, etc, or, simply just Diy from cashier?