IMO this seems like a terrible idea.
If it's just a taller spring then the dampers extended length will be the same. Essentially, you would be driving around at full droop constantly. Not only would the ride quality be bad, but if you hit a pothole or such the car is just going to fall into it because the wheel can't travel downwards properly. I'd also imagine the spring is going to block (all the coils smash together) if it's taller and has more coils but the damper is compressing fully. The spring isn't adding travel, it's just changing where you sit in the travel.
The bump stop should be the end of travel, not the spring. You're asking for a load of additional load on the spring arm. I just can't see any situation where this would be a better alternative to the "puck" kits.