If someone doesn't wear a lid into the nets then they're fair game in my opinion. As bowlers we need to bowl like we would in a match and if someone in a match bats without a helmet then we as quicks have a responsibility to try and hit them!
Depends what your nets are like. Most nets here in Australia are concrete with synthetic grass over the top. They play completely differently to turf pitches, where a reasonable amount of games are played.
So while i agree with 'as bowlers we need to bowl like we would in a match...' its actually quite difficult to bowl at training on concrete like you would in a game on grass.
Provided your facilities can cater for it, bowling full pace is really a must, both for batsmen and bowlers.
Also, love the fast bowls mentality here.... Lets not try and bowl decent lines to get the batsmen out, lets knock his head off!!!
Although, a mate of mine, as a fast bowler, believed there were two qualities to be a fast bowler. 1. Have a protruding lower lip & 2. Have the ability to drag their knuckles on the ground behind them.