I am much more interested in detailing of beams meant for only gravity loads only and these are being affected by lateral forces, as these beams are part of the whole structure.
In case ur object is carry out analyses and design on gravity loads, it's OK.
U can employ lateral loading to the SAFE...
In my opinion, u can have strip of any size/ geometry. During designing the rebar are being evaluated & distributed as per average moment capacity of the section, so the layout of strips should be logical otherwise u would have very illogical results.
Stage construction modelling is the way to carry the analyses. If the routine be developed for the one as u r curious, it would increase the processing time tremendously and could only be implemented for certain highly special nature of works.
In Etabs reaction out at column is based on loads from all floors.
Since for export to Safe only single floor can be worked out, and on using option of floor loads only ( this is the valid option for the design of the floor), the reaction at column would be for the loads on the floor only...