I'm not sure if I totally understand your data structure. However, the simple answer to your question is just to do a second set of loads and concatenate them onto the relevant tables, or consider if the query:
field X.BEGDATE<=VDatePrevyear or field X.ENDDATE >=vDate
Will work for you.
I am also wondering if your begin date and end dates need to be separate in all the tables? If they are common to the Key, maybe have one table with all the values concatenated - Key1, BEGDATE, ENDDATE - and then you can use an Interval Match to create a calendar table linked to both date fields.
The problem is not very clear, but from what I understood I have few suggestions:
Why do you need to create separate model for current and previous years? You could create just one model and add some kind of flag to distinguish between current and previous year. Hope this is of some help...if the problem is something else, please provide more details (if possible with an example).