In terms of what's workable here, some talking points.
Floor plate of existing, approx. 12000ft2
Separation distance to east 3.5M
Separation distance to south: ~7m (aerial photos on an angle)
If, you assumed something much taller would be built here........(for argument's sake); and assumed the applicant would accomodate 1/2 of the standard separation distance (not necessarily the case)
The floor plate if you were to taper to 12.5M in from the east and south lot lines would be in the range of 4,500ft2