Due to the way the integer features are used within VA, Int64 would require yet another data type. That would need to be put on the backburner for another time.
In the meantime, I have added {DECFORMATUSER}, {DECINVFORMATUSER} {INTFORMATUSER} (and their default value counterparts) to the token parsing process. They will allow you to pass in C# format strings for each type. For instance, to have a decimal formatted without decimal places and with commas, you would use N0: {DECFORMATUSER:myDecimal:N0}.
This will be in the next beta.
On a side note, {INTFORMAT:} is old and rigid - needs to be deprecated
