I think you have it in a nutshell Gaz.
The asparagus brother has a legitimate safety concern.
He also over-rates himself, as he hasn't done all that much in motogp with signficant opportunities, which are probably more easily available to Spanish riders than those of other nationalities in the current motogp milieu, not that there is any evidence of which I am aware that Brookes would have done any better with similar opportunities.
Aleix clearly over-rates himself (IMO) and really does seem to have a passport advantage as for a guy to have over 200 races and only 2 podiums is not (IMO here before people jump up and down) a great investment.
We in this forum (and others) are often critical of riders such as Redding for example, but Redding has 18 podiums and 4 wins in his GP career (2 podiums in MotoGP compared to Aleix's 2 in total) and yet it is Redding that battles to maintain a ride.
As for Brookes', well he did finish top 3 in the World Supersports and I reckon could have made an ok shot with decent equipment at many categories (same for many riders), but to be fair, he is more a journeyman and that is what makes him interesting. He will ride BSB one weekend, Suzuka the next and then a road race even the next all on different machinery plus he will then often appear at a dirt event somewhere else and at no point does he try to pull ego (when local in Aus).
But you allude to something that should scare the living .... out of DORNA which is that few riders are coming from non European countries and making it to the GP classes which should be sending alarm bells as the talent is there, but the dollars to start buying rides to become noticed is not .