Yet another distro?
Not to sound crude or downing anyone but is creating an entirely separate distribution really the best way forward?
I mean, there are several distributions which could be up to this task as they stand even some which could be highly tuned (Gentoo, Arch anyone?) surely the better way forward would be to use an existing distribution and add any required packages/features as an additional repository/ppa?
At least this way your applications are not tied to a custom distro and you can recompile them / package them for other distributions as and where required.
If support is an issue then you could go to someone such as Red Hat who for a subscription fee would be happy to provide any and all technical assistance where required. In addition they have a lot of experience in that particular field (supporting businesses).
I just feel that a new bistro isn't necessarily the best way forward. I understand that they may need specific applications or security tuning, but all of that could be easily accomplished by simply adding an extra repository and tuning to an existing bistro (you can roll your own install media/live image where required to avoid tuning each PC)
In addition, those doctors who are already using uBuntu would only have to add the PPA to their existing installs, avoiding a reinstall and in some cases confusion.
Just my 0.02 GBP.