Thanks everyone for your replies. Reading these have really made me reconsider how to approach the harder difficulties going forward. The reason why I thought it sounded like a good idea at the time was because that even if equipping something like a heal tome could still jack up my evasion. Not to mention that having recover can be huge as a powerful heal, but in the end it might just get in the way.
Falcon Knight Byleth sounds reasonably attainable considering that I would work on lances and flying primarily as well as swords so I could go lets say Commoner > Myrmidon > Falcon Knight > Swordsmaster/Wyvern Rider > Falcon Knight. I also wonder if weight -3 would also be worth it for the sake of reducing the weight penalty? I bet it's not worth it but just a thought? I know Warmaster Byleth is easy to obtain too because of Axes and Brawling and brawl avoid +20 helps byleth's avoid when punching things.
Also I am also wondering if battalion vantage + battalion desperation are also worth using? I know that regular vantage requires your base HP be under half health for it to activate. But the battalion version of that only needs to be at 1/3 of its endurance. I know Chaz Aria mentioned that Defensive Tactics reduces the damage your battalions receive. So would it be worth trying out or are they just a waste of space?
So Falcon Knight Byleth would something like Sword Prowess Level 5, Darting Blow, Alert Stance+ Defiant Avoid (maybe?), and maybe either Lance Prowess Level 5 (incase of swordbreaker), weight -3 to reduce weight penalty since enemy paladins and falcon knights from what I read have it, or maybe one (or both) of the battalion skills? I know Dimitri has the famous battalion vantage + wrath combo which makes him among the best critical hit units in the game and I think no one else gets it that combo.
And Warmaster would be something like Brawling Prowess Level 5, Death Blow, Brawl Avoid +20, Quick Riposte and maybe Battalion Desperation?
Otherwise I think that without going too crazy in investment I could just go Assassin and keep jacking up sword and bow since I know having a long range attack without fear of retaliating is invaluable. Plus having all that speed, accuracy, 6 move, stealth and swordfaire are enticing options.
Thank you guys once again for your input