Right now the church I've designed has a nave that is cruciform. The floor is open save for four columns to support the central dome and the 4 towers. The windows up higher are all into the nave of the church.
Also, the wings on either side of the narthex (the octagonal central piece) are actually the bathrooms, stairs and elevator (to the basement, in case of bad weather) The windows on the front are actually not windows, but rather recessed parts of the building to echo the windows as well as to provide something more than just an empty front... Someday those could probably even house icons.
I think i've heard there is a possibility they would the like the two connected. I think we could also get some exemptions from the code for having them connected.
Floor plan of the building shown above:
The two triangular spaces could be storage, or connected to the wings and be used as hallways to the bathrooms or hallways to the stairs/elevator.
As planned, I believe that the height of the current nave would be about the same as what it is now, however it will seem taller/thinner because the roofs of the four corners drop down about 10ft from the central cruciform roof.
Also, the transepts on the north and south could probably be widened a bit. But I figured that is one feature of the church that is nice, especially since the nuns often stand in that area currently. Possibly have one transept for the nuns, and the other transept for the choir.
Also as a side note, the four towers on the corners won't have windows, rather, they will have a smaller dome-type structure in the interior with lighting. This would save money as well as cut down on the amount of support the towers will need. Also, more windows = more uneven heating and cooling during the year, which contributes to higher bills due to A/C and heating costs.