Without giving a lecture on basic physiology, the basic answer is that you already get a concentric, eccentric and (brief) isometric phase with traditional lifting.
If you're training hard, lifting heavy you will be developing your fast twitch fibers. A key point though is that you don't really need to worry about fiber type. If you train heavy and explosively, your type I fibers actually adapt metabolically to behave more like type II, and likewise, if you consistently train with prolonged endurance activities, your type II fibers will behave more like type I.
The general recommendation is to perform the concentric, positive phase as fast as possible while under control, while performing the eccentric negative phase at a slower, controlled rate. This might mean anywhere from 2 -4 seconds.
It's worth experimenting with this stuff though. Some philosophies incorporate a distinct 1 second isometric pause between eccentric and isometric phases. Some do a slightly longer eccentric.
Sure, focusing a lot on eccentrics will create more muscle damage and especially soreness, which may lead to greater hypertrophy simply as a result of greater time under tension (volume). I'm not sure that it makes an enormous difference when volume is taken into account.
Bottom line: lift heavy, and progress all your lifts. Get strong as hell. Explosive positive, controlled negative. Experiment with tempos and pause reps if you like. As long as your lifts are still progressing, this stuff is all fine.