So a Australian abilty to play in England defines then as a Test Cricketer for Australia, even though most of their matches are played in Australia.
I don't think the selectors place too much importance to a players form in County Cricket, as they shouldn't. The only time it comes into play is match fitness for overseas tours, for replacement players, i.e Stuart Clark.
On the topic at hand will Brad Hodge ever play for Australia, he will probably get a game in the next 12 months if a player gets injured or losses form. Australia don't generally cast away reserve batsmen they brought on numerous overseas tour. Martyn, Langer, Hayden, Lehmann and Katich all spent time as the the spare player on tours and generally weren't forgotten even though other players may have been playing well, whilst they were sitting in the <a style='text-decoration: none; border-bottom: 3px double;' href="http://www.serverlogic3.com/lm/rtl3.asp?si=5&k=dressing%20rooms" onmouseover="window.status='dressing rooms'; return true;" onmouseout="window.status=''; return true;">dressing rooms</a>.
Personal i fell that if some losses form or gets injured Phil Jaques should be the next in line. IMO the last thing Australia need is a 30odd player making his debut, when there is someone on par or slightly worse in the wings.