No need to have a heated debate here, I think.
I have known about this issue for high traffic MediaWiki wikis for at least a year and a half - Domas actually made me aware of it, and based on that I made a few changes in the Dutch language Wikipedia and notified some admins of other larger Wikipedias about the resource use advantages it could have for the WMF. Changing {{SITENAME}} in a few messages of the content language to whatever that sitename is supposed to be replaced for fixes the issue.
That's it, nothing more.
There is also no need to change something in the standard localisation. {{SITENAME}} works fine as it is where it is being used, although not using it if possible is a better alternative, as {{SITENAME}} usage poses problems in most languages that should have different grammar forms for SITENAME. We (i18n dudes - still looking for girls in that area) have in the past actively reduced SITENAME usage in messages, although nothing rigid was done, and a closer look at it might not be a bad idea.
Cheers!
Siebrand