Hi maiki, and thanks for your post. I’ll try to answer to all your points and questions as better as I can with my poor English 
Hardypress should not discourage upgrading; countered by a lot of people don’t upgrade anyhow.
You are perfectly right. Upgrade is a good practice that should be always done, no matter what. But in case you do not can/want to upgrade, because you are legacy or for any other reason, with HardyPress you don’t need to. It is not mandatory. With a static copy online you are safe anyway. In my use case this was a lifesaver several times.
Hardypress supports a single contact form, I suggested some others.
We are working hard to extend the support for other plugins. This is just an MVP.
Hardypress encourages Disqus, better to discourage comments altogether, or have other options available/encouraged/tutorial’d.
After your precise previous feedback we totally removed Disqus from the new website. We are still looking for a good (possibily free/opensource) alternative easy to integrate in a static site.
How does the search feature work? Both curiosity, and for client services, I’d like to know.
When we create the static copy, we scrape the website and index the content. As simple as that
What happens when storage, transfer and contact form email limits are hit, for a given price tier?
You still can access your wordpress, but you simply can’t deploy a new static version online.
How do the “deploy user roles” interact with WordPress users and roles?
It does not. HardyPress allow WordPress editors to enter the WordPress admin area even if WordPress it is turned off, so they don’t need to enter the HardyPress dashboard to bring WP to life. In the same way, the “deploy user roles” allow selected users to deploy a new static version through the WordPress admin area without access the HardyPress dashboard.
If you have some other questions, feel free to ask
Claudio