the tragic bit of the hunger games series is that everyone is lowkey sleeping on the fact that plutarch heavensbee, or heavensbde, is the one character who managed to pull a rebellion right up under snow’s nose, found out about district 13, got victors in the districts and spies in the capitol to his side without getting caught or anyone informing the president about this, and came out on top even after the war.
long story short, I've usually felt more drawn to side characters because there is a lot that remains unknown about them and one can become creative themselves. meaning, katniss, peeta, gale, and haymitch never felt like my characters. when thg released, I pretty quickly hopped into the rp-scene writing and contemplating about those characters that received fairly little information. and for the most part, that's been capitol characters simply because the capitol, too, felt a lot more underdeveloped compared to district 12. sure, there's other districts, but I fairly rarely create original characters, and in the rp scene interactions are important. every major character visits the capitol, so that's the perfect place. besides, the caption feels close to the western society that I live in, so that's been interesting to headcanon, too.
that leaves my choice of characters to enjoy with capitol characters who are not very well developed. at first I really liked caesar, and then plutarch grew on me as an extension to caesar (I headcanon them as friends).
as with many other characters I enjoy -- caesar included -- I like those that do not have much of a backstory except for some pillars that one can work with. plutarch is a mysterious person, and that's cool! you have a lot of wiggle room in how he's supposed to be and that's fun, no? take katniss. the fandom has written an immense amount about katniss. but--unless we go for canon divergent--she will always have a set backstory, a set goal, a set life. plutarch's motivations are unknown to us, we barely know how he grew up and how his life used to be before the 75th. there's so many open questions that we don't have in the same amount with a well-developed character.
specific tidbits about plutarch that I like are
he's central to the rebellion. without him, the whole thing might not have existed. what's his role in there? when did he come up with it and why? how did he find 13? how did he pull off the 75th?
he's mysterious as a character and leaves plenty of unanswered questions. questions that I've mentioned in the first point, but further than that I'm curious about him as a person. he was the CEO of capitol rebellions (tm), but he's had a lot of courage to do what he did. did he have personal motivations? how did he became so knowledgeable about the time before Panem?
he is vital for my other characters and the overall story I want to tell. my first character was caesar and ever since then I've written about caesar a lot in relation to plutarch. for caesar to be a rebel, he needs to know plutarch--and I like to seem them as best buddies, opposites entirely because one thinks with his heart and the other with his mind. there's also my original character, virgilia snow, who is married to president snow and who falls in love with plutarch and thus has a major rebel right by her side. plutarch feels vital for all the stories about rebellion in the capitol and why shouldn't he! he's a major character there.
I approach thg as a dystopian literature, not a ya literature. this feels like a vital difference. ask me what book recommendations I have that are similar to thg and I will probably just list the dystopian classics to you like 1984 rather than divergent. and like in most of these, the character meets, believes in, or founds a rebellion. those characters are usually the main characters. while katniss was important and is a great and well-written and brilliantly conceptualised character, she ultimately was used by the adults around her. but at the same time, plutarch did found something, he created a network of people that made a system possible that could use a figurehead like katniss. to found that system (or join it, but in my hc he founded it), it takes extreme courage and competences to figure out who to trust and who not to trust. it's exciting hearing more about that! and therefore plutarch--and characters like caesar who join the rebellion--are characters whose stories are worthwhile and interesting.
PSH lifted plutarch up. we all sorta know that there's great actors, and PSH was one of them. I at times like his performance even better than how plutarch was written--in the books he feels rather like a know-it-all while the movie!plutarch has a tad bit more empathy and just overall has more emotions--book!plutarch was happily running around 13 before the bombing while movie!plutarch shat his pants, more or less. PSH really gave plutarch more of a fleshed out character.
I cannot say that I really truly want a book from Collins, simply because I have my own thoughts about him and will ultimately be disappointed in small or--worse--big ways. but it is fun to just conceptualise and think about what I'd like to see her write :)