Thank you for your feedback. Below I will explain the rationale behind moving to Subversion 1.7.
Subversion 1.7 has been out for a while now and features a far better working copy format than version 1.6. This is especially noticable when doing a lot of file system changes, such as adding and removing directories. Unfortunately, this new working copy format is incompatible with the previous format used in Subversion 1.6, which means that tools based on Subversion 1.6 (TortoiseSVN 1.6, Mendix Business Modeler < 4.1.0) can only work with 1.6 working copies, and tools based on Subversion 1.7 can only work with 1.7 working copies.
The Mendix Business Modeler includes its own Subversion library. Thus, multiple Modeler versions can be used side-by-side without problems. This means that the average user will not have any troubles, as the Modeler uses the working copy format that it is compatible with.
For most users no separate Subversion client is needed, as the Modeler handles changes to the file system automatically. However, in some cases it can be useful to use a separate Subversion client such as TortoiseSVN to manually manage files or to resolve file system conflicts. It depends on the client whether two versions (i.e. 1.6 and 1.7) can be installed side-by-side. In the case of TortoiseSVN, I believe this is not possible. However, several workarounds exist, such as installing a command-line Subversion 1.6 client alongside TortoiseSVN 1.7, using a VM that has 1.6 installed, or even uninstalling and reinstalling different versions when the need arises.
We realize that this will be inconvenient for people who need to use a separate Subversion client and work on projects in different Mendix versions. However, we wanted to bring the improved experience that Subversion 1.7 offers to our users as soon as possible. Because of the incompatibility between tools based on Subversion 1.6 and 1.7, there was always going to be a transition period when using multiple Mendix versions side-by-side. We hope that the improved experience makes up for the inconvenience.
We also thought about this. When Mendix takes decisions like this it would be nice that we know this before implementing it.
Edit after comment Achiel:
Don't think so. Why? Because the release notes are available on the release date of a new release. At that moment you will be confronted with the svn upgrade. So in order to use 4.1.0, I need SVN 1.7.x. and need to take a decision. I don't know if it's possible to install two different versions, but if not, that would be an issue for me.
Because most of us are involved in older projects which are not compatible with SVN 1.7.x. So we're facing a new challenge. I'm only saying that we could think about this earlier, if we knew the SVN upgrade was coming :)
Thanks Benny for the extensive explanation