Don’t want to join app marketplace

I have been trying to find an answer unsuccessfully to this. We are a Saas Company developing an integration between our software and hubspot. It is meant for our existing mutual clients, and we are a niche software and there is zero benefit to us to be listed on the marketplace. We are going to want to enable way more than 25 clients when we launch the integration. We will of course still develop with OAuth, but is there any middle ground so that we can have a higher limit without being listed on the marketplace?