If he wants an American, why not Newgarden?
Because he is soo far from Super License Eligibility it's not funny.
As of right now he has 1 real choice with 1 other far better choice if things work out.
Rossi will likely get in the top 3 this year in GP2 which will give him the Eligibility but it's taken him far to long to get to this stage in GP2 it's worth little as an acheivement with the Experince and familiarity advantage he has on most of the field.
RHR has the points but he is too old and will never be considered, plus he is having a terrible year.
The Best choice if he wins the Indy Title which will give him the points is Graham Rahal, currently 3rd in points and a Driver who has shown Elite speed on Road courses, he would likely be leading the championship now if not for having a Honda engine, he has had some rough years in the past but most of it was with Poor Cars, this is the same driver that got 5th in his Rookie year in Champcar as an 18 year old.
He is 26 which a bit on the Older side for a rookie is still a good enough age to build a career from.
F1 is far more complex than Indy... and in my opinion more demanding. That's most likely why Haas is looking to take experienced F1 drivers with young Americans as a later plan.
Indycar is far more demanding from a Track perspective and the car is much more physical.
No Power Steering makes it hard for other open wheel drivers to just jump in the series and do well(See Barrichello).
I know Bourdais/Andretti is used as the main reason for why people think indy drivers are not suited for F1 but there are some reasons why I can say otherwise.
1. Bourdais won his titles in a car that was by far and large the best in the feild against a grid that had been depleted of Talent(a driver like Power driving Aussie Vineyards rubbish and still able to fight for Pole consistantly)from IRL taking the biggest two teams (Penske and Ganassi).
2. It requires a driver good at both Oval and road course to be in title contention and this can muddy up the standings on who would be more suited to F1 which is Road course only.
Bourdais while dominating was never in the same league as a driver like Power when it came to outright speed on Roadcourses if given equal equipment, I have no doubt if you had put him in F1 in his 20s he would of performed like Montoya.
Indycar is a much different Field of comparison compared to GP2 and the like, in thise feeder series most of the Talent is Raw but there tends to be much more drivers with Substantial talent compared to Indycar, however Indycar drivers are significantly more refined as the drivers have made Careers out of that series unlike F1 Feeders so overall the drivers are at a Higher standard as they are at their peak performance or close to it, but not the best standard for F1 who are willing to work with the unrefined to find the Elite.
Allthough like the case with Drivers such as Power, Dixon etc some of these Elite talents never got the chance to show themselves in F1 so they went to Indy.