I see your point. But I do think that a map builder can be, if they so choose to be, impartial to a point. I can see the fault in thinking that I can be fully impartial to my design... the best I can do is guess at what a skilled veteran can do versus a relative newbie player and then keeping in mind the objectives and goals for each team design a scenario that does work for as many as possible.
Again, if you design a scenario with a specific set of targets (say tanks) then you should provide the aircraft and weapons that will eliminate them. With options for skilled veterans that may perhaps be more rewarding as well as options for less skilled players that still work fairly well. The difference say between using a Hs129B-3 (and that lovely 75mm gun) to crack open some T-34s or IS-2s versus a Ju88A-4 with a 2000KG bomb that a more newbie player may not necessarily land the marksman hit on the tank with the 75mm but he can still potentially take out the target with a little skill and luck.
Fighter versus fighter tends to be highly skill based with some degree of fighter performance on the table as well so the best I can do is provide a couple of options that should work well on both sides with a variety of pilot abilities and go from there. For example I find myself tending to put the A6M Zero on a lot of Japanese scenarios even when higher performing types are available. The N1K2J is essentially superior but its a little trickier to handle in places and so many newbie players do better with the Zero because its easier to handle... so I make sure that option is there. Slowly they graduate to the more complicated type. Depends on what they are up against too!
I may be flawed in my thinking here but I attempt at least a modicum of humility and attempt to be as unbiased as possible. Both teams should have the tools available to win. The rest is definitely up to the skill of the team. To be honest, I'd like to fly on either side and win or lose on my teams merits.
As for MODs...well that's a whole other discussion
