Alright, questions that arise when you're reading for too long.
Alright, starting from the top of the problem. The Lend Expertise ability lets you grant a bonded ally a combat feat you know for 10 rounds. Simple enough but it brought something to my attention. Can you grant them a weapon proficiency that you have? Example, Grenade Proficiency is a feat, granting (obviously) proficiency in grenades. As an Envoy I have grenade proficiency but I do not actively have the feat for it.
A different example, and perhaps a bit more problem raising is Small Arms Proficiency, which most people have. To my knowledge I can still take Longarm Proficiency the feat, even though I don't have the actual feat Small Arms Proficiency because my class grants me that proficiency, even if it doesn't specifically give me the feat. And I get it.
If you were given all of your proficiency feats, most (if not all) would start with at least 3 feats. Basic Melee, Small Arms, and Light Armor Proficiency. That would automatically give pretty much every character access to Adaptive Fighting from the get go. However then it becomes iffy. If you for sure don't have the feats, then you'd have to take them to Lend Expertise, despite that you don't need them.
More confusion to add. At 3rd level, most classes gain Weapon Specialization as a bonus feat for all the proficiencies their class provides. This is a feat, as it specifies it as such, however it specifies for each. So the Envoy has Basic Melee, Small Arms, and Grenades. Does this grant them Weapon Specialization: Basic Melee, Weapon Specialization: Small Arms, and Weapon Specialization: Grenades? That's three feats, and again the out of the box requirement for Adaptive Fighting.
Back to Lend Expertise, regardless of how one manages to get it, Adaptive Fighting is a combat feat. If you lent your bonded ally Adaptive Fighting, would they use your three selected feats to pick from, or would they pick their own three to choose from? Alternatively can you give them your current active Adaptive Fighting feat?
I think by this point it's obvious how I broke myself. Some things aren't feats, and may or may not work with some things, while others are feats and may or may not break requirements. I couldn't find anything in the FAQ about feats at all, granted the FAQ hasn't seen any updates since Pact Worlds where the archtype with Lend Expertise exists.
My RAI on it all. You don't have the feats for your proficiencies. Lend Expertise can lend a proficiency from your class, even though you do not have the feat. You get one Weapon Specialization: [u]CLASS NAME[/u] Proficiencies feat at level 3, and it can be used as prerequisite for Versatile Specialization, and Adaptive Fighting. No idea on Adaptive Fighting+Lend Expertise interaction.
I also have the odd question of why light armor proficiency, small arms proficiency, basic melee proficiency, and weapon specialization are feats at all when every class gets them natively. Possibly for the intent of future classes that would lack them? Or playing Pathfinder classes? They are options though that in Starfinder's native system, no one would take. No character lacks those 3 proficiencies, and because it gives you a bonus feat for specialization you don't need it since you can get Versatile Specialization for and additional proficiencies you decide to pick up. Only way you don't get it min level automatically would be if you multiclassed 2 levels per class to avoid it.
Where does this ability come from? I have never heard of Lend Expertise
I see it now, sorry it took a lot of reading to get to that part. You should probably cite rules and abilities when you use them to save people some trouble. Checking it out.
Yeah RAW it looks like you can't grant proficiencies only feats, so if you obtained a proficiency through an alternate means you couldn't grant that, as the way you learned it is weird and can't be taught in this manner.
In general I don't see a problem with granting someone a feat you don't have if all it does is grant a proficiency and you have that proficiency. Unless you don't meet the requirements for the feat. But this gets into sticky territory so I'd typically avoid it. Mostly I was interested to see if someone could grant a drone the ability to be proficient in armor but alas. Explicitly disallowed.
Weapon specialization does not apply to grenades per the feat on page 163.
My bad, that is true. I was just listing through Envoy proficiency without thinking. Most of my points remain valid however, it's simply one less potential free feat towards Adaptive Fighting.
A new interaction question came up. To do with Versatile Focus and Lend Expertise.
Of course you need Weapon Focus to apply for Versatile Focus. Lend Expertise requires that the bonded ally qualifies for the feat. So if the Skyfire Centurion has say, Weapon Focus with Basic Melee Weapons and Vesatile Focus are they limited to only giving Weapon Focus with Basic Melee, or since they have Weapon Focus at all, and/or Versatile Focus, could they give Weapon Focus with any of their proficient weapons?
I vaguely recall there being a ruling somewhere that the class weapon proficiencies do count as feats. Not sure where, though.
Well, they're all listed in the feats section, and you can use them as prerequisites for getting other feats, such as using small arms to get longarms.
I don't really see the value in discriminating between the feats you get from your class and the feats you get by spending your feat slots.
I'm working on a Dwarven Operative/Exo-Cortex Mechanic who will end up with the same proficiency set as a Soldier by level 2, just from her race and class bonuses. I'd rather not have to figure out and track where she got each of those feats if I don't have to...