I've taken the point about "more reasonable number to welcome both community members and
outsiders" (since Jan-Bart, originally designed an outsider expert claimed proudly to be a part of community [cf. Board Election 2007] and another appointed ex-life member Jimmy is even considering to run for the next Election, this argument makes a sense, I think), "more diversity and room for resignation". However, since all Wikimedia Board of Trustees are volunteers, while they take many responsibilities and take care of things in reality not only the highest level of management, but still they are volunteers, it is rather difficult for me to figure out how this increment can help avoid "putting too much constant pressure on volunteers".
Marginally off-topic, but I would advise against Jimbo standing for election and would keep giving him an appointed seat. He would inevitably win any election, so it is effectively an appointed seat, so having a meaningless election just takes away an elected seat.