It's strange how you view bouncers as defensive bowling, it's an established way of attacking a batsman and a vital part of any bowler's arsenal.
I've always said that in my experience bowling short, sustainedly, is just about never a good idea. The odd short delivery is fine to mix things up, but more than one every couple of overs or so is just a waste of deliveries - good batsmen almost
never get out to them (except on super-fast pitches like the old WACA, old Kensington Oval and old Kennington Oval) and even moderate ones only relatively rarely do.
There are times when wasting deliveries is fine, like when the ball isn't doing a lot and you're waiting for it to start doing some more. But when it's new and you should be looking to swing it, wasting deliveries by bowling short is very bad bowling.
I have a different view of new ball bowlers. For me, a new ball bowler's job is to put the batsman under pressure immediately, keep him on the backfoot, choke his runs, and set the tempo for the rest of innings (and obviously, to take wickets in this process).
As I say - for me, the new ball is useful because it swings (conventionally), properly, more than at any other stage in the innings. If you cannot swing or seam the ball, or choose not to, you have no right bowling with the new cherry IMO as you're wasting it while others could be doing what a new-ball bowler should be.
Keeping a tight line is essential even if you are attacking.
I don't disagree with this at all, defence and attack are not two polar-opposite things where bowling is concerned. A good line is essential to both. I'm talking purely about length.
Bowlers like Wasim and McGrath excelled at that. If you tried to blast the batsman's wickets out like its the last 10 overs of a one day match, you run the risk of letting the swing get the better of you or being thrashed if the pitch is unresponsive, removing all pressure and letting the opener dictate terms.
If the swing is getting the better of you, you've got options to reduce it (use a slightly different grip or wrist position) or to make more use of what swing there is (eg, use the crease, go wider and closer, aim for a slightly straighter or wider line). A good swing-bowler should always be happy to see the batsman (opener or otherwise) playing shots, as if the ball is swinging your chances as a batsman are always reduced the harder you go at the ball. In any case, swing isn't all about swinging it onto the stumps - you're aiming as much if not more for the edge of the bat.
As for the pitch, swing is irrelevant to that, because it takes the pitch out of the equation. Swing is all about the ball (with atmospherics also playing a part, though the best swingers can swing a good ball regardless of atmospherics).
Even with Waqar's matches against England, his success generally came with the old ball, the term 'toe crusher' came from those series.
He certainly had more success with old ball than new but he did try to use the new ball and succeeded on no shortage of occasions. I can't remember Wasim ever taking that many wickets in his opening spell because he rarely even seemed to try, he was just interested in bouncing the batsmen.