You can either have 2 views for the record (one view showing the full form and the other one showing half the form {remember to also include all required key fields) or you can split your database structure into 2 different tables with a join and a 1-1 relationship (ie user record, office record).
Using Fabrik 1.x will most probably cause you no problems as it is stable.
If you really want to go for Joomla 1.5 and Fabrik 2.0 you need to be aware that database structure is likely to change when stable version is out and...So i guess it depends on how complicated your application is..
A 3rd option that i havent tried yet and just occured to me is that you could have both Joomla 1.x and 1.5 installed and display Joomla 1.x pages with Fabrik 1.x forms inside a wrapper module of Joomla 1.5. However this will be a waste in your hosting space both in terms of size and number of files hosted...