(Better) IPv6 support. For those that don't offer it, start. For those that do, offer more than a /60

Inversely, better IPv4 support: as a startup ISP you probably don't have much v4 space so you'll be relying on on CGNAT. But in the US at least, users have come to expect public IPv4 addresses. If that's too cost-prohibitive, at least make them available upon request or as a value-add.