It seems insane to assume that all genetic manipulation would lead to superior specimen, let alone ones with superior ambition and both the capacity and desire for superior evil. Most of the manipulation is probably done to give complete losers at least some hope for parity; this is what was done for Julian Bashir, and probably also what was done for Spock.
Genetic manipulation in the name of evening out the odds is not really forbidden. In "Dr Bashir, I Presume", the Admiral who throws the book at Sisko and Bashir specifically says that the laws exist to prevent the creation of supermen, and Bashir himself specifies that the laws prohibit certain specific techniques. Elsewhere, the plot specifies that Bashir was indeed augmented not merely to cope in the society, but to be better than other people, thereby going against the spirit and letter of the law. Lots of specificity there - and little in the way of general rules.
If the Bashirs had settled for mere parity, they might not have broken the law at all. It would depend on whether the specific, banned techniques were absolutely needed for parity, or whether parity was otherwise attained and they were just a little extra that the Bashirs approved so that their boy could get an edge over his classmates.
Besides, genetic manipulation for the creation of superior specimen is apparently perfectly okay when it's done in the name of science, under controlled conditions. Or that's what seems to be the case in TNG "Unnatural Selection". Makes sense, too. Slashing people with knives is a big no-no, unless you are a surgeon. For all we know, it's the fact that the treatment was given to Bashir that was illegal, not the treatment in itself.
As for whether pon farr would increase the prowess of the fighter, I don't see why it should. Generally, hormonal aggression in the nature does not produce better fighters. It merely produces more aggressive fighters, who may be at a disadvantage for their very aggression. Hormones may give you stamina (or more probably make you ignore that your stamina is failing you) but they are less likely to give you skill or even strength.
Timo Saloniemi