I think work capacity and alternating periods of static holds and explosive movements are essential training strategies for goalies.
I do some traditional interval training on a bike with goalies, like I do with all hockey players, but I have a greater emphasis on iso-holds. I usually use a squat iso-hold, or a split squat iso-hold with toe pull (raising the heal slightly on the lead leg and pulling the ball of the foot into the ground to activate the hamstrings to a greater extent).
Another idea I stole from Brijesh Patel is to alternate static holds with explosive movements. For instance, hold a squat position for 10s, then perform 3 max effort vertical jumps. Land and hold the squat position for another 10s, then perform 3 more jumps. Go through this cycle three times, for a total of 30s of holds and 9 jumps. This must be done with caution and your athletes must have a good understanding of proper and safe movement. A safer variation is to do it on a slideboard. Maintain a squat position on one side for 10s, then perform 3-5 rapid “back and forths” then stop and hold the squat position, etc. If done correctly, this is about as goalie-specific as it gets.