I am going to add something that has nothing to do with the Holsteiner mare lines.
Decades ago, when Arabian pari-mutual racing was starting in the USA, the most expert non-breeder (Gladys Brown Edwards) commented that Arabs with high trots (fore arm level) were the most athletically capable racing Arabians, unlike the TB where high action tends to slow down the horse (Man O’War being the big TB exception, he galloped high.) She was not commenting on jumping ability at all, mainly because Arabs are proven to “kill the TB jump” as well as the TB speed. Back then the high trotting Polish Arabs were beating the domestic bred lower trotting action Arabians handily. Of course the Polish horses are EXPENSIVE now, especially the good Polish Arab race horses.
As a hint from what I’ve observed, give up the pretty head, the pretty head won’t do your athleticism any good and if it is emphasized too much the leg joints get smaller. This is also a problem in the TB and ASB, pretty heads shrink the dimensions of the knee and hock joints big time, even worse than what happens with the Arabian.