My general approach against an unknown opponent (until I learn their moves and figure out an approach geared around them) is to establish myself as the more aggressive player and try to maintain an edge in small pots. This is of course a popular tactic. However, I think it creates two distinct advantages:

1. It gives you a small but constant chip edge that can only benefit you if you're a better post-flop player
2. It creates mistakes in your opponent's play

Fnord - you characterize regular raising - unfairly, I think - as chip-spewing and jamming. I know the players you're talking about, but I don't consider myself one of them. I like to raise most of my better hands for value. There's nothing wrong with getting more chips in the pot when I have an advantage in equity. I don't raise with some of these hands, at times, to mix up my play and, as you say, induce horrible mistakes. Obviously stronger hands are the best candidates for this as they are the least susceptible to unexpected beats. An opponent who is sick of your raising crap might decide to take a stand with a weak top pair right when you are playing meek for a change with pocket aces or kings... that's the ideal situation that the aggressive play sets up.

I agree with you that you don't necessarily want to play huge pots against opponents you can outplay later when they decide to gamble, but I wouldn't think of a raise from 20 to 60 as setting up a huge pot, either. Stacks are 1500 - is a pre-flop pot of 120 (when he even calls) really a monster? If you take down just a few of these in a row without a showdown you make your opponent nervous. The next time they make a big mistake, you'll have them outchipped and thus be in prime position to take advantage.

You seem to advocate patience as the main method of letting opponents make errors... I think raising them more than they raise you is another way, and it often can force errors in play faster.

It also has the advantage of boxing most opponents into a very transparent gameplan. Very often they decide to counter your aggression with trapping, which means any time they hit a flop hard they check-raise or slowplay. Once you learn to sniff this out, you'll rarely lose a big pot to your opponent, and the rest of the time you'll win 75% of the hands.

I do think there is a valid need for change-ups, sometimes within a single game (you can't be too predictable with any one type of hand) but more related to the opponent you play. Obviously if someone is determined to NOT let you be the sole aggressor, there's no point getting into a chip-spewing war. But I've found that even though I'm just a medium-aggressive heads up player, the average opponent online will let me run the show and sacrifice small pots to me almost as often as I want them. This really works to my advantage unless they get a very lucky hand early on. Given 10-15 minutes of play against this type, I'll have them outchipped at least 2:1 most of the time. Then it's just a matter of being patient. I actually tend to slow down as i go along... it's easier to steal a lot of pots early, build a chip lead, and then patiently exploit their weaknesses as they open up the aggression and try to come back on you.