You stop taking flavor text seriously when you read nonsense like "Fighter is the best fighting class". And you stop making arguments about writer intent when you notice that many times the rules contradict themselves even within the same book (for example, undead creatures that lose particular organs can no longer use the senses associated with those organs, but skeletons are neither blind nor deaf).
A lot of the writers didn't know what the other writers working on the same projects were doing. Flavor text and mechanics text seldom agree with each other. Besides, ultimately the point of a game is to have fun with it. If extrapolating literal interpretations of what you're given to bizarre conclusions is what you enjoy, you're no better nor worse than a player who uses the texts as a mere guideline framework to build their own shakespearean drama cause that's what they enjoy.
I also agree with you that the writers of these books clearly didn't know what was going on in other books, and/or didn't care to explore all of the rules interactions. Although I fail to see how someone could write up Aptitude without thinking of how dumb it would be to have people using grappling feats with a blowgun. Or the game balance problems with letting people use feats that were supposed to go on a light mace (low damage, low crit chance, sucky weapon) on a great crossbow instead (missile, high damage, high crit, cool exotic weapon). Just bad game design.
Weenog:
Before reading the spoilers, know that I don't mean you any ill will or entirely disagree with your interpretations. These are just my arguments why your build wouldn't work, and I feel the arguments themselves are at least as qualified as yours. The second spoiler is the more succinct argument and probably the better one, but I didn't want to just remove the first one after I had gone through the trouble of writing it.
Aptitude doesn't change the words of feats, and while you might think it makes the feat apply to the weapon no matter what the feat said, it still applies to what weapon it says. You can reload a hand crossbow as a free action still applies when you're holding the Great Crossbow; you can still reload the hand crossbow, it's just not what you're using. Notably, it specifies "using." Obviously there's room for argument here, but honestly it assumes using the weapon normally. This nullifies the hand crossbow autoreload. It doesn't nullify Lightning Mace, however, but the RAI of Lightning Mace requires a separate weapon in each hand, so Lightning Mace nullifies itself. Even if you want to argue that holding a weapon in two hands allows you to use the feat, the feat doesn't actually specify when "attacking with the Light Maces"; you simply must be using a Light Mace in each hand. Roundabout Kick uses Unarmed Strikes which aren't "weapons"; they are natural attacks. "A monk's unarmed strike is treated both as a manufactured weapon and a natural weapon for the purpose of spells and effects." This line suggests that they are weapons as its specified as a weapon in both descriptors, but the common name for a natural weapon in every other application is "natural attack." As well, feats that are applied to "weapons" specifically call out Unarmed Strikes as acceptable exceptions to their rule. Weapon Focus: "Choose one type of weapon, such as greataxe. You can also choose unarmed strike or grapple (or ray, if you are a spellcaster) as your weapon for purposes of this feat." The feat has to explicitly grant exception to unarmed strike, otherwise it would be ineligible for the feat.
(The previous arguments kind of became superfluous when I read the Aptitude description. They aren't wrong... well, in some cases they are, but in general they're applicable, if unnecessary.) Aptitude only applies feats that "affects the use of a particular type of weapon." Lightning Maces and Roundabout Kick don't affect the use of a weapon, they provide bonuses if something specific occurs. They aren't capable of being applied by Aptitude. Hand Crossbow Focus will work, although sketchy, as the feat itself affects the use of the ability.
As neither Lightning Maces nor Roundabout Kick function for the build, it wouldn't hit more than 10 times in a round. Well, I suppose you could create a specific set of circumstances to enable Lightning Maces, but I don't think swinging miniature Lightning Maces at air would do much when attempting to wield two weapons in one hand.
In contrast to Weenog's build, my build is far simpler and involves the use of only one additional book as opposed to several.
Swashbuckler 3/Fighter 2 get's you 4 feats + Weapon Finesse and Int to damage when using light weapons. The majority of thrown weapons are light, so those ones that are gain the benefits of Int to damage. However, my build loses Str to damage because of a class feature of Master Thrower, which my build enters at 6. Master Thrower's "Palm Throw" allows throwing 2 weapons with each attack, but you cannot apply your Strength bonus to either weapon. It has a floating extra ability (can use Deadeye Shot for bigger multipliers on crits or Two with One Blow to hit more enemies), and then it caps off with Weak Spot, which makes attack rolls with Weapon Focus'd thrown weapons target touch AC instead of total AC. The prerequisite feats are pretty simple; Weapon Focus with a thrown weapon, Point Blank Shot and Precise Shot. You can grab 2 of the 3 from your Fighter bonus feats. This leaves you with 1 floating feat. You can also do Fighter 1/Bard 1/Swashbuckler 3 and go into Dread Pirate by skipping Precise Shot until you're level 6 and instead grabbing Quick Draw, but this equates to a loss of 2 feats (1 from the lost Fighter level and 1 from not getting the free feat from Master Thrower).
A build I've wanted to do has been Bard + Dragonfire Inspiration with a sonic dragon tied to the feat and then cranking up the Inspire Courage feature, and capping off with Dread Pirate. You can activate your Inspire Courage at the same time as a Dread Pirate feature that does the same thing, however they won't stack normally as they apply the same kind of bonus (Morale). However, with Dragonfire Inspiration, you convert the effect Inspire Courage grants to something else, enabling them to stack.