what are some tips for constructing a dubstep drop (melodies, variation, number of instruments or instrument combinations) and how do i incorporate diminished scales without sounding too weird in dubstep, trance, etc

Just to clarify, do you mean actually 140 bpm dubstep or electro? For both of them anyway I would recommend having some sort of chord progression in the drop to work around, rather than just spewing out a load of harpsichord and square wave (which a lot of people seem to do). What most people do for the actual structure is having a two parts to the drop; an A drop which is more "Gritty" and generally what you would expect from dubstep, and a B drop which is more melodic (or it could be gritty as well but with more variation), so the full drop will usually be around 32 bars (16 bars for both the A and B).