This may or may not be something I do, depending on a few things, but I am curious none the less.

I have the shitty old grey K100 coils and would like to replace them and the leads soonish. 

However I have on hand a nice set of K1100 coils.....(that I may be swapping for new style 100 coils)

To use them, I would also need to use k1100 leads and spark plugs to suit, as well as modify the wiring connections to the coils from the loom.

So, assuming this is all done - correct plugs and leads to match the 1100 coils - is there any potential of causing damage or excessive wear or anything bad at all to the bike and its systems by using the 'out of spec' 1100 stuff on the 100?

(the reason if not already obvious for doing this, is that I would need to buy new leads anyways, but If the 1100 coils work, I dont need to buy coils)

I evidently dont know enough about this to figure it out. 

Any ecectrical gods want to chime in, or someone who has been using this setup for years without issue would be welcomed too

measure the primarys of the coils floyd  and you will see

Spark plugs are matched to an engine and not to a coil. Is there a difference between K1100 and K100 spark plugs?

Yes the R which denoted a resistor and that IS matched to the coil and not the engine.
What is matched to the engine is the heat range and a projected electrode
K100 D7EA
K1100DR7EA