For the pause idea, maybe you have to wait 20 seconds without being able to move or shoot to pause once you click the pause button, and then wait 20 seconds before unpausing so you can't unpause as soon as someone is in firing range.
There should be some better guns that cost 0 cash but maybe a ton of coins like an assault rifle that is about the same as Assassin but costs 60000 coins so you can get it from tourneying. + if you want this