Can't you get longer springs to keep that from happening? I had to get longer springs on my E90 setup when the initial drop was a little too low. Same spring rates, but just taller.
Well it is not that simple, the shorter springs they provide are designed to give the desired ride height range already, so if you go with a longer spring you would also have to go much softer which defeats the purpose of the upgrade in the first place. This is also why you cannot add a helper spring with this kit, because even though it fully compresses, it still adds about an inch of height, which again takes you out of desirable ride height range.
An actual coil over strut is able to use a helper spring because the lower perch is about an inch lower, so they can add the helper spring and use similar spring rates/length and also stay at a desirable ride height range. This kit is designed to work with the stock struts and because of that the lower perch is higher so you don't have that space for a helper spring, and if you try to go with an even shorter stiff spring you will limit spring travel, which causes another problem. I know all of this because I have the GC kit and have been tinkering with it, a lot. I am very happy with my setup, but it wasn't exactly plug and play.
The issue mentioned above about it falling apart when you jack the car up really isn't a problem, the parts are designed so that when you lower the car it all slides right back into place, and it does do that every time.
There is no perfect option from what I can see, if you want to maintain the DCC with height adjustment and significantly stiffer springs, you have this option or the Bilstein B16 and with that kit besides the cost, uses 4" springs and I saw where if you want to use camber plates (and you do) the spring rubs. So now you will want to find a 3" spring that will work with that setup so... However, if you don't care about maintaining the DCC function, then a full coil over system is definitely the way to go.
With the GC kit I went one step further and found some thin 1 mm thick hub rings that were the right size for the upper and lower perches. This allowed me to press the spring into the the perches and the whole assembly stays tightly together even when the car is raised. This was not actually necessary but my OCD kicked in and... (see pics below)
So now when the car is jacked up the entire assembly stays tightly together like this:
Also the 034 dynamic mount probably works well with the OEM bearing but with the GC adapted strut bearing I was not happy with how it seated so if you are familiar with those parts you will notice I did a bit of modification there as well.
So what's it like? Well first of all, would I like custom shock valving that matches the spring rates? Sure, but I talked with Bilstien about that, and on there DCC dampers they do won't do it. From what they tell me with this spring rate they would actually decrease the compression damping and increase the rebound damping. So it is not ideal, but honestly it works a lot better than you would think. One thing I noticed is that the difference in ride and handling from comfort to sport is much more pronounced. Driving at low speeds on a bumpy road it is firmer and bounces you around more, but it is not what I would call harsh, there is more motion but it always has a bit of spring to it so it doesn't beat you up like a car with really stiff dampers will do (for reference I have driven a focus RS and this is way better than that). The best part is when you drive aggressive/fast on a bumpy road, that is when you will really appreciate these springs, it is so much better than stock. The thing I find about the stock suspension is that it is fairly complaint (for a sports car maybe but not great IMO) but when you hit some major bumps at speed it easily bottoms out in a very harsh way. I found that far more unacceptable than a firmer bounce at low speeds. Now I can hit major bumps at speed in the middle of a corner and the suspension just soaks it up and never bottoms out accept under truly rare and extreme situations. Oh and no weird noises, clunks, or anything like that.
So like every other option it is a compromise, but for $600 and I get to keep the DCC adjust ability, it is the ideal compromise. Just keep in mind if you are going to start mixing and matching components, it won't be a simple plug and play.