On one hand, the use of vanilla DnD systems are sound and commonplace, and allow for more universal understanding of what can and cannot be done. As well, it allows for me to make judicious and supposedly-clever decisions on how each species can play off one another—for example, how Crewpeople would have Strength and Intelligence bonuses, but a massive Charisma cut and awful saves for vs. Charm, to reflect their utilitarian status. In this case much of the work would be done already, and my job merely reskinning and adjusting terms and numbers to fit the setting.
However, a literary technique that I admire is that of 'the form reflecting the function', or in this case the calculative bits of a game being built to properly fit around what it is attempting to play out. Of course, this isn't to mean that a system should be built from the ground up every time for each and every new test-concept brought to the fore by some upstart little blogger with no established say; but I have the inclination to make Tidewaters more difficult, and slightly more independent.
One method of doing so would be through the creation system brought up in my initial post about the setting, which suggested a mash-together quality of subsystems: the replacement of hit points by regenerating endurance points and dramatically terrible wounds, the use of traits at creation and after major events to have a character's growth be more dynamic than a meteoric rise of stats-points, the simplification of stats to use smaller numbers with each value being more valuable, and such.
The intent would to be a game that has most everyone be in a precarious position when faced with the dangers of the world, but not overly-focused on combat.
But I don't know, honestly. Any suggestions from anyone who is reading?