That or just carefully set up the preset beforehand. Or do you mean as the first purchase of each map? The presets system is still relatively vestigial, presets aren't carried on once you close the game (or is it each map? idk, point holds) but they're useful for getting lots of the same thing in one game.
However I suppose that point is redundant if you only have one favorite loadout, as they're carried on between purchases anyway...
Wow that whole post was redundant, smallified for those that don't want the clutter
What paul proposed was closest to what you want I suppose, but you'll need some lua knowledge first.