I feel at home with the database (PostgreSQL, whichever version), and PHP (whichever version). I've worked with Yii before but not with CraftCMS. I learn fast, I won't have any issues with you legacy system either. I'm a single developer and the project is biggish but I'll manage in about 2 weeks. Pick me and I'll deliver you an easy to maintain, cleanly structured solution. Plus easy communication and a free German translation!
So I'm going to summarize a bit. A legacy application (which serves primarily as a marketing website), being replaced with more modern systems, while also introducing a proper separation of concerns. The new marketing platform (based on Craft CMS) introduces a new questionnaire module, which:
* Will currently work in parallel to the existing PDF solution.
* Will support CRUD functionality (create, read, update, you want to leave the delete out?).
* Will render as HTML forms with validation rules (backend and frontend?)
* Will be augmented with a report generator (I'd prefer to introduce a separate plugin, which you might later use for other report generations)
* Will handle propagated credentials (probably single sign-on mechanism)
* Unclear: Configuration of the questionnaire or just the questions are in plain text format (Configurtion: YAML, JSON or INI, just translations: PO files (prefer standards)). Do you want to keep the whole questionnaire configuration or just the questions in the text file?
I'd love to work on that ;)