Hi Danijela,
I just read this whole thread, and it has been an interesting 'ride'. I hope you have learned from it, and others too.
I recently bought a Sinar e22 back, and was really drawn to this system because of the adapters. I love the fact that I could put the back on a Rollei 6008 one day, and something like a Hasselblad SWC the next. Not to mention various view camera options, or upcoming bodies like the Hy6. I feel quite free to choose my platform.
By comparison, a friend of mine bought a new P30 in Sweden with Mamiya mount and then wanted to change to a Hass H mount only two months later. He was charged around $4k to swap the mount, and now he is still stuck with one mount.
I shoot people mainly, so I can't be of much help with specialised architectural applications. However, I can add a few comments in reply to some of your posts:
The upcoming Hy6 is not a brand new body. The name is new but it is in effect a Rollei 6008 AF 'D'. It is important to realise that this camera is built on a proven platform and should not be regarded as a higher risk than a Hass H3, for example. For some reason people feel secure in the Hass H platform because many others are using it, but that is very flawed logic (think sheep!) You should also be aware that Hass H has some problems with the camera locking up. You need to remove the battery to reset the camera and continue shooting. You will find various threads on this. Also, there are many reports of the 50-110mm zoom lens falling apart. I am not trying to start a brand-war, but just pointing out that the assumption that Hass H is proven and totally reliable and that the Hy6 is a complete unknown is quite FALSE. The Hy6 will also offer a rotating back (great feature which I already enjoy on the 6008), faster lenses, faster flash sync, and a wider array of lenses and accessories, and of course you can start using the system today with a 6008 body, as I do.
As for the Capture One and Brumbaer tools, you are free to download them both and play with some raw files before buying. Both these tools are very simple to use. I had to email Thierry once about an undocumented feature (revealing hidden menus), but apart from that I felt comfortable about the workflow in one hour. I had been using Capture One Pro for years but the transition was pretty painless.
You are also free to use Brumbaer DNG converter and Lightroom, without using Capture Shop. Using a Macbook Pro I was taking about 5 seconds per raw file to convert to DNG. Pretty quick. Would be a little longer for the e75 files, of course.
It will be interesting to see what Exposure bring to the table. It was scheduled to be released by about now, so I hope it's not far away.
The suggestion by someone in this forum of a quick-release system for the Sinarback was inspired. Changing adapters now is doable in a few minutes but it makes me a little nervous. Perhaps Sinar could think about this, and take an already useful feature (back adaptibility) to the next level. We can then leave the adapters permanently on the camera bodies, and move the back around in seconds.
Good luck with your decision!