And this is where definitions get wooly! You're leading towards training at lactate threshold, yes? To increase the level of power that the muscles can produce without going kablooey?
That is indeed not the same as the amount you could, say, leg press, which is limit strength. Limit strength (over a certain amount) is not necessary except in specialised circumstances (I'd argue that it's useful to put down some monstrous kaboom to get the 'jump' competitively; jump isn't a feature of TTs, tri or distance riding, but it is in velodrome and pack racing).
The hill grind sounds like a great way to build LT power.
Bike-only workouts are a great way to build muscle imbalance too. The traditional "mighty quads = kneecap tracking woe" is resolved by doing free-weight leg work, which hits the medial glutes and inner thighs as well as the power muscles, and keeps things together. Up to about bodyweight, there's a role here for weights -- and there's that youtube of Lance doing just this.