Feature Requests or Advice on Choosing another Tool

I am evaluating a support system for a client and found the Support plugin here is missing features we really need. So I'd like to add those as a feature request - and I also would like to get some ideas on other plugins that may work the way we like.

Must:
- self hosted (no other service like zendesk)
- email piping, so users can send requests by mail
- no client login required to submit/edit tickets
- can easily be integrated in the overall site design
- knowledgebase

Should Have:
- auto suggest answers before submission
- easy to work with (e.g. HTML5 drag and drop of attachments)

So, the support plugin here lacks of two fundamental things for us: email piping and "anonymous" ticket submission.

At the moment we prefer osTicket but it isn't very easy to integrate it in our WP-based site.

Does anybody have any suggestion?