I am really disappointed with how CA have treated Liu Bei. It starts off ok but then goes fast downhill.
Lady Gan (she could be added as an ancillary as she was concubine, but give her the ability to have kids) should join as soon as you get the Tao Qian choice event as he met her whilst visiting that region.
Sun Qian was approached by his friend Zheng Xuan, who recommended he join Liu Bei after Tao Qian's death. He should join as a unique character when this event occurs.
Mi Zhu, Lady Mi, Cao Bao and Mi Fang should also join at this point in history as they were all serving Tao Qian at this time.
Liu Bei should get an event straight after Dong Zhou's event as traditionally Lu Bu left and asked Liu Bei for protection. Leading to betrayal by Cao Cao sending Liu Bei off and leading to the death of Cao Bao.
This would lead to Liu Bei appearing in Runan.
Upon arriving in Runan we should get Zhou Cang joining as he came there with Guan Yu.
Liao Hua and Chen Dao should also be available to hire at this point as legendary Vanguard and Sentinel too. I say legendary for both as Liao Hua was vanguard to both Guan Yu and Jiang Wei and somehow survived, and Chen Dao was rated as second best officer in Shu-Han after Zhao Yun.
This is also the point where Zhao Yun should join with his event.
Guan Yu and Zhang Fei should both get their wives too.
Too much of the story is missing. This does not apply to just Liu Bei though the same could be said of Cao Cao and others. All of this would help with the feel of the game, as Liu Bei was chased around the map by Cao Cao for years.