+ Is there a need to save state between sessions?
+ Why in the cloud?
+ What needs to be secure?
Cynically, eight hours a month is probably closer to ten counting time spent dealing with Windows updates.
At eight hours a month, I'd wonder whether the overhead of shared responsibility would be worth the effort versus just having one person take responsibility. In an activity highly dependent on standards and accuracy and consistence such as accounting, I'd suspect errors to correlate casual or infrequent or disinterested users and adding layers of implementation complexity such as the cloud to increase the odds of errors as well.
So my gut would be to just put one person on the task. If information had to be shared, I'd look at storing the data centrally and distributing copies of the executable. As the third option, I'd package the data and OS in a VM image and treat it as a file under version control. For something with sensitive information, the least desirable option would be a running Windows installation accessible from the internet.