But this is just Edelgards perspective on the whole. She says the nobles abuse the common people and drain them of everything they have and that might be true regarding Duke Aegir, Arundel and some other nobles but the game also goes out of its way to show that here are nobles who not prey on the weak. Lonatos men follow him because he convinced them as a Leader same for Rodrigue and many others. The meritocracy she wants to build wouldn´t just solve all problems and instead would create new one. In this regard i side with Dimitri the world she wants to create just benefits the strong ones. And i know you will disagree with me on this point but i guess it is like the Meeting between these two both have valid points for their Beliefs but i could never support someone who only thinks killing other people is the only way to achieve your goal. It´s a simple matter of beliefs and i think you can´t value the life of other people like this for the *greater* good. Regarding Rhea, Edel pinpoints all the blame on the church but the church neither encouraged the caste system nor did they abolish it they simply stood aside. Not the best attitude i agree but i don´t think Rhea would have opposed a social revolution in the Empire. And from there she could have easily reformed the Church in the Empire. Regarding Edelgard and TWSITD in Part 1 i´m not sure how much power she upholds appereantly enough to wrestle Duke Aegir out of his own lands and enough to field Imperial Soldiers at the Holy Tomb. She has the Death Knight at her Disposal and Randolph and Ladislava. So i dont think she has no power to oppose them but again the game is not clear on that.
I wondered this myself already but i just thought disaptching *mysterious soldiers* would have alerted the Knights even more onto their plan of Total War since in Chapter 1 or 2 we already get to know that Rhea and Seteth are suspicious of something. And Kostas confirms that his job was just to kill as many nobles as possible in his convo with the Flame Emperor. The theory you mentioned could be possible i also read that people think Edelgard is drawn to Byleth because of her Crest and him housing Sothis. But unless we get more info about her actual thoughts i take Kostas words for the truth. He has little reason to lie to his Contractor.
In this regard you might be right but she always fights with all means necessary and is willing to do everything to achieve her goal and since this is the only route where she is offered pardon I simply would assume she´d rather live to maybe have another chance than just dying. Naturally i didn´t assume Dimitri would let her roam free but his route, in my opinion at least, focuses very heavy on the topic of earning your redemption even if it costs you your life. Dimitri first thinks he owes it to the dead people then he swears to live so he can redeem his past sins by serving the living. Gilberts support show a similar mind set. Rodrigue mentions this aswell. I think out of all people Dimitri could have been the one to actually still give her a Chance despite political uproar. But it´s just speculation.
Vile might be a strong word but i do think her methods are not morally grey in the least. She is willing to kill innocents even before she declares war on everyone and that is in my opinion hard to justify. And i know this game is all about if you beleive you´re right stick to your ideals but that is in my opinion a very dangerous attitude. But i have to thank you, you gave me some new things to think about.