I'm A Banana
Potassium-Rich
All well and good, but I was trying to get more of a feel for technology from a mechanics standpoint rather than a fluff standpoint.
As I mentioned, you have an engineer class, which almost guarantees that you have some sort of class abilities for them. I'm curious where you went with that, if you've gone there or even thought about it yet.
AAaah. My apologies.

Anyone can craft most of the items in FFZ with the right combo of feats and skills, of course. Machinists are simply the BEST at crafting. And because of the "KISS" mantra I've adopted, I wanted to make sure that crafting was not an excersize in accounting and bookeeping based on prerequisites, skill ranks, time, and gil. Instead, the inventions "just happen."
To clarify it slightly, it works more like the Craft Points mechanic in UA than anything else. You have a finite number of things you can craft, and a limit on the power of those items based on your level (no 1st-level sub-oribital death-beams, no effectively infinite supplies of low-powered items, either). These items are crafted more-or-less automatically. Mechanists get bonus items in a way very similar to how spellcasters learn spells -- they're simply awarded based on levels.
What power they have, then, is defined by the type of items available in the campaign. By default, there are things for high-level mechanists to craft that do resemble stuff out of sci-fi (space ships, teleport pads, time loop paradoxes, etc.), but that's at the pinnacle of a long line of items from potions to airships, to constructs and even monsters. Edgar's tools make appearances at relatively low levels (the chainsaw isn't even really that powerful of an item, though it rocked in the game). These are limited in much the same way as spells are -- by a "Tech Rank" rather than a Spell Rank (Tech I, Tech II, Tech III; rather than Wizardry I, Wizardry II, Wizardry II). This also helps define what a Mechanist can actually control in abscence of skill rank -- Int of 10 + the level of the tech.
Now, because I've wanted to avoid introducing a mechanic that is always better to use than a standard attack (I know this goes against FF canon, but I think there should always be a place for a standard attack), these items do have to use fuel of a sort, if they can be used in combat. Firing an airship canon or powering the chainsaw can use up MP (though generally substantially less than a similar spell) in addition to delays or other limits.
As for abilties other than invention (which covers the tools and Use pretty well), the Mix ability will appear in some form, as will Rikku's famous ability to disable constructs in combat nearly instantly. There's going to be a nice handful of abilities from FFX-2 and FFT's alchemists, too. Mix is going to be tough because of the impossibility of documenting all possible item combos, so will likely focus on the results of the Mix ability, and become something of a random rod-of-wonder style table. There's also item synthesis (a popular staple of the genre by now) to be included, where you'd combine some things to make others, though this will probably fit more in the realm of AP than anything else.
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