Not to completely shat all over your idea, but... </pants>
Reducing call-in time doesn't help at all unless you are massively floating resources. At 480MP a pop you would need to have almost 900MP in the bank for it to be possible to call in a second thing as soon as the cooldown expired. I would recommend picking cards that don't rely on poor resource management but that will help support your game style.
Well, my job here is done. <pants>
No single bulletin will impact your gameplay performance. AT ALL. It might one day give you that extra 2% to kill one dude faster, but it won't give you a winning formula. Ever. Not with those percentages.
I've seen the "Ultimate" Bulletins, which merge the benefits from two bulletins into one (freeing up a slot). Even if you could stack these, with the original ones to stack say, a 4% damage with another 4% damage, it is still very small.
I've said it before, and I'll say it again: Smart positioning, strategic thinking and situational awareness of the battlefield will get you victories more often than any bulletin or APM possible right now.