The Problem is not as much Emperor's Xian character, but the breakdown of the system and authority of the Emperor..
Pple like Dong Zhuo/ Cao Cao dun start out with ambitions of a new Dynasty ,.
they gradually became bolder , as they're drunked with power and realise the emperor inadequacies..
As for what kind of Emperor Liu Bei, would be, it depends on which Liu Bei we're talking about in the 3k timeline..
Dun forget that Liu Bei's Char and aspirations grows ..as the Novel goes on
Only an older and wiser and more established Liu Bei have what it takes to restored a bit of authority , but it'll be a slow and delicate process to pry power away from the Lords, les we have another armed rebelion ..
a Younger, zhuge Liang-less, Liu Bei , would do well to preserve what little bit of the authority the Throne has , but theres' a high chance he might slipped into Liu Shan mode..
Just being emperor , Xian has as much currecny as Liu Bei. ,atleast with all the "good" chars in the game..
And Xian shown that he's smart and have abit of backbone, but is powerless as he dun have a personal military Power as back up..
So.. a pre- Peach garden Liu Bei is as powerless as Emperor xian ..
Magister mundi sum!!