It's certainly thinking outside the square & has it's merits but I'm not lining up for a ticket just yet.
Instead of the whole lap, have you thought about breaking it up into 3 sections? When you go to the La Sierra page, it gives you the option to 'Practice' and then choose from SS1 - SS4 or full lap. My advice would be to choose 3, making them 1 each of Racing Hard (0% surface water), Intermediate (25-50% surface water) and Wet (75-100%) all with grip set to Real.
Besides that, my only other concern is, not being a fan of Standard cars, I've only got the Audi because it's a Premium. Do I want to spend millions on the other 3 cars? Considering I'm not online & have to slog it out the hard way to earn my credits, taking into account their earning ability & how much time I'd spend in them, that doesn't hold a lot of appeal to be honest