Keeping the same set of stewards for every race would undoubtedly improve consistency, but may not improve justice (e.g. you simply get stuck with a set who are consistently harsh, or consistently lenient). I'm not sure if that's an improvement, really.
At the end of the day common sense must play a part, and I think now more than ever, with ex-drivers on the panel, the stewards need to retain the ability to use their own judgement, rather than thinking that some sort of regulatory bible can be written that will cover every eventuality.
http://www.fia.com/en-GB/mediacentre/pressreleases/wmsc/2009/Pages/wmsc_111209.aspx
FORMULA ONE
F1 Stewards
A smaller permanent group of F1 Stewards will sit with experienced former F1 drivers to provide a permanent panel of three FIA stewards, together with one steward representing the National Sporting Authority, to deal with F1 at each Grand Prix.
There will no longer be a non-voting Chairman and each group of stewards will elect their own Chairman amongst themselves for each race. Utilising video and radio exchanges they should aim to reach decisions very efficiently.
The current observer programme for F1 stewards will continue, and training, distribution of decisions, and an annual meeting will be encouraged to raise the quality of decisions in this permanent group.