The IPCC is being reviewed by the Interacademy Council (which represents dozens of national science academies). And they're taking public comment. This might be a good chance to get some improvements. The comments form is at: http://reviewipcc.interacademycouncil.net/comments.html
If you can't think of anything, here's what I wrote:
- The IPCC needs to report more frequently. Interim reports, or even annual updates would be very useful.
- More focus on possible tipping points. Especially estimates of sea-level rise from glacial melt, and estimates of non-linear responses to warming.
- More transparency with the process - especially which representatives are making which changes to the finial release.
- Stop being so conservative. Offer an your analysis, and be prepared to defend it when it gets attacked by the fossil fuel lobby and governments.
- Work with science communicators. Create a lay-person's version of the report.