In order to determine the maximum of a set, a conditional or sorting operation would be required. DIESEL supports conditionals, however cannot accept nested fields; Formula Fields accept nested fields, but do not support conditionals or sorting.
One possible solution might be to use a Field which references a global AutoLISP variable which is assigned the latest revision; the variable would need to be defined on startup & also following modification to the attributes in question (which would likely require reactors...) - although potentially feasible, this is a messy solution.
