When creating a new feature branch, the current version asks the user for the branch name and an optional commit message.
In the case of a single-project repository layout, that works just fine: a new branch is created under "/branches" using the provided name, and the source code is copied directly into the new branch; besides, a new job is created with a name composed by concatenating the original job name with the name of the new branch.

In case of a multi-project repository layout (http://svnbook.red-bean.com/en/1.0/ch05s04.html), the location of the new branch must be composed by concatenating the branch name and the sub-project name. This can be achieved using a simple workaround: specifing the complete location of the new branch in the "branch name" input field, e.g. "mynewbranch/projX". This approach is error prone and one drawback is the name of the new job which results in a long and possibly non-intuitive name that must be changed manually. (e.g. "projX-mynewbranch-projX")

In addition, since we've adopted a development process that forbids direct development in trunk, we need to tag the trunk version when creating a new branch, to track back the state of the trunk in the moment the new branch is created. In particular, we have a tags/dev folder in our repo for that kind of tags, and a tags/rel folder for the effective released versions.

To address the needs of this scenario, I suggest to implement more fields in the "new feature branch creation" page, to give the user the means to control the newly created job in a more fine-grained way, including the opportunity to create a tag while creating the branch.
Let me know if this feature can be useful for the community, I'm going on with the analysis to provide a more concrete proposal.
I'm available to take in charge the development.
Cheers

Verny