SaaS model are pretty interesting if you consider to give part of your source code. Referring to the risks i would list you some more important one, focused and at the point:
- Assumed your publicly traded company is vers skilled the most users will find it more difficult and less appealing to work with.
- It makes sense for you to use proprietary parts if you can do it in specialist fields maybe.
- If with this decision you are technically giving less Support but more focus that's should be an advantage. Meaning decreasing direct your operational costs
- Cloud software is slightly different than conventional software. As a general rule, you don't get access to the source code, even if the hosted software is built entirely on open source software. That may not make the software proprietary, strictly speaking, but it doesn't give you all the benefits of open source. In that sense, the benefits of using the "pay for what you use" software as a service model may outweigh the disadvantage of not having access to the source code (http://www.cio.com/).

If is not enough get a local lawyer to help you out. Let me know if you need more.