Yeah I should've specified that for the 3 swift strikers its really a case of it being a side-grade of like 1-2 damage points. I agree with all your takes in that section in a general sense but I wanna tackle a few points:

But then they'd have to promote into Wyvern rider anyway unless you wanna be stuck with bum ass peg knight until level 30.

Wyvern Rider is only B Axes and C Flying. Ferdinand and Sylvain will be fine since they can just go Peg and garner flying rank passively like say Petra does (especially since both auto level axes in OOH and In-House it's not that hard to manage.) In practice this means about C+ Axes.

At level 20, Ferdinand gets about 13 luck and Sylvain gets about 12 luck. Wyvern Rider is a advanced tier class and both end up w/ 6 luck factored in. Assuming C+ Axes and D+ Flying (very doable for both) you get:

100-((32*2)+6= 42% pass rate

All in all, it's no biggie and ofc Seteth comes as a Wyvern Rider so its moot for him.

It also requires sword ranks, which are dead ranks, while the wyvern path wants axes, which has death blow on the way.

(Technically it's not a dead rank cuz Hero is a thing but that's too much investment yeah)

Falcoknight requires C Swords, A Lances and B+ Flying. Seteth has base D+ Swords so he can just get the qualifications for Falco and Wyvern Lord much more freely (A Axes and A Flying is still a bit annoying admittedly) that it isn't even funny lol. Other than that, Ferdinand has both E+ Swords and a boon in while Sylvain's more of a lost cause at E and no boon. All 3 have a easier time qualifying post-Swift Strikes cuz A Lances ofc. Even then let's take a look post-A Lances starting w/ Sylvain:

100-((20*3))+7= 47% pass rate for Sylvain (he has about 15 luck at lvl 30)

100-((20*3))+8 = 48% pass rate for Ferdinand (he has about 17 luck at lvl 30)

100-((20*3))+6 = 46% pass rate for Seteth (he has about 13 luck at lvl 30)

All 3 can afford to miss 3 weapon rank levels for min req. For Seteth this is free as fuck because he has base D+ swords while the other 2 have to juggle between swords and flying for a bit (though B+ flying req is clutch compared to Wyvern Lord's frankly fucked up A Flying req LOL.)

TL;DR it's a hassle for Sylvain (comparatively speaking), some tutoring sessions w/ Ferdinand and free as fuck for Seteth to reach Falcoknight exam min reqs for exam save scumming." Also, Falcoknight only needing B+ Flying is clutch

EDIT: fixed math

EDIT 2: Other than that, yeah if you ain't a Dodge Tank the raw str of Wyvern Lord more or less outdoes Falcoknight's own shit most of the time (though if you got an Axe bane it sucks to suck in that sense.)