Well, if Kimi is going to use the new system he needs to find a suitable setup for it. Grosjean cannot do it for him so it must be Kimi himself doing the driving. The track itself shoudn't be a problem because Kimi has always learned new tracks very quickly.
It depends on how much this system changes the characteristics of the car, I guess. If its that big a change, then yea, I can see why they'd have it only on one car. If its not, then its just a gamble. Yes, maybe Kimi will benefit from having driven it for a time already, but he may also struggle on the weekend due to lack of running with the new parts.
For instance, its always funny how people react to drivers at Ferrari testing out new parts. If its Massa, its cuz he's a guinea pig. If its Alonso, its cuz he's the favored one. In reality, there's positives and negatives to either situation that you've gotta weigh carefully. I'm just wondering if perhaps Lotus have gambled wrong? Its a big weekend and they might be thinking that if things dont work out, they were never favorites anyways, but if they do, then they'll look like geniuses. There's a very thin line there sometimes.