Disabling/Enabling Modules Parameter RHEL

No, I've never seen the issue. But it sounds messy. This may be a hosting support issue. If the host pushes a specific kernel version and they manage the R1Soft install, shouldn't the host have a working hcp module available or be able to walk users through the steps needed to get things working? If anything, you can try hcp-setup and upload the relevant info to R1Soft's build servers. I've never had to build the module locally, but I'm usually on distro kernels or slightly-modified distro kernels.

At what point does it make sense to depart from the OS-provided kernels and packages when the upstream maintainer has broken an important feature?

"At the point where the vendor's kernel or packages are so horribly broken that they impact your business" is my general answer (coincidentally this is also about the point where I say it makes sense to start looking at ways to depart from the vendor relationship).

Basically as you and others have said, RedHat seems to not want to patch this in their distributed kernel (for whatever reason). That pretty much leaves you in the situation of having to roll your own kernel (keeping it up to date on patches yourself, maintaining your own package and installing it on your systems with Puppet or similar, or running a package server that Yum or whatever they use today can reference), or taking your marbles and going home.

Yes I know taking your marbles and going home is often an expensive proposition -- switching OS vendors is a huge pain, especially in the Linux world where the flavors are radically different from an administrative standpoint.
Other options like going totally CentOS are also unappealing (because you lose support, and you're still getting essentially RedHat's code built by someone else so you'd still have this bug).

Unfortunately unless enough people (i.e. "huge companies) take their marbles and go home the vendor won't care so much about screwing people over by shipping bad code and not fixing it.