I agree with @kspika the user case for this is widespread surely? The huge amount of Trello users that have Hubspot and vice vera.
In our company it would be excellent to push a closed win from our Hubspot CRM straight onto either a ‘board’ or ‘card’ in Trellio. It would also be great to see and edit a Trello checklist within Hubspot and see a certain amount of information back from Trello so that an account exec can easily see the status of a clients project. A similar integration for Jira would go down a treat too. Zapier can never do these things as well as an Atlassian/Hubspot collaboration could 
I also agree that unfortunately the Hubspot projects tool doesn’t yet seem be a suitable alternative to Trello and not close to Jira. I think that if this issue was surfaced with more users who also use Trello/Jira in order to deliver their sale in someway, they would value this and it would further cement them into both your respective platforms.
How easily are you able to survey users on these type of requests?
Thanks