The main issue I see is Single Sign-On being gated behind enterprise pricing, and a "please contact our sales team" option no less. Big enterprises can happily pay whatever you ask for SSO, but this mainly hurts the medium-sized businesses that only set up SSO if it's convenient; if it costs a lot more, they'll settle for the reduced security of username+password auth. If anything, supporting the big 3 identity providers (Google, M365, and Okta) on the Pro plan would be better than charging to have any form of SAML/SSO.
https://sso.tax/Also, do you have plans to offer a discount or donated version for nonprofits?