Following your advice I managed to update my Building Generator.
The final version has 6 user inputs for better control:
-number of base floors
-height for the base floor
-number of top floors
-height for the top floor
-on/off switch for height variation (my take on this one was to use the info you provided and add this random height on top of the current building height; so if you have an initial input of 2(base)+5(top) and the spline ID is 5, the total number of floors will be 2(base)+5+5(top)
-on/off switch for interior lights (to use for night shots)
*I've also added randomized curtains in the style.
Thanks again for all the help!