Don't over look Targa just because it's too big to learn quickly - I spent about 3 weeks solid tring to learn it for my GPL rank (Video
here if you're curious) and still don't really know my way beyond Cerda well enough for flat out driving so no-ones' likely to have much of an advantage....
I'm up for all of the tracks mentioned - I'd suggest aiming towards either a 2 or 3 lap race of Targa or to use the method UKGPL did when we held an event there a few years back = An extra long qualifying session and to seperate all the cars out nicely when leaving pits.
Positions are then calculated from qualifying times as opposed to race positions (This is closer to how the race ran for real aswell - I guess if someone wants to spent some time with a calculator you could work out peoples complete 'race' time over the 2/3 laps to have a fully authentic result....