What purpose do you think Shamrock serves in One Piece and who is possible here?
Shanks replacement in the story after he likely croaks after this arc to show his full potential, would be my guess if i need to, but just more than "zoros token HK sword dumbo opponent." Could be alot of other things but the point is he is way more important
1. He was in the final spread, so far for 90% percentage its confirmed, and for the rest its heavily implied, that they have their own agenda. We are already getting the vibe, for example, that for garling he seems to have higher ambitions and seems to be different than the rest of the gorosei. It makes sense that he was in the spread being the same faction, like for example Coby who is also in the same faction as akainu but still drawn there because he follows a different path to akainu and is important
2. Shamrock potential was compared to 2 armed shanks and shanks would only reach his level AFTER he got a deep sea contract. So shamrock has a portrayal and hype that transcends Shanks, who is crippled, and oda refuses to answers sbs question if cripple or mihawk, zoros pre-final arc opponent, is stronger
3. Narrativly Shamrock being introduced on elbaf clearly as a tease for bigger things to come while the focus the whole arc was on shanks is just bad
Like legit cap take that A) shamrock will come back to elbaf b) will have a full fight against zoro at all things, at any point before the final arc