A newbie questions

How's much good in using a high-command King (especially Byzantine's one) in the battle field ?

I can deduct the basic pros & cons as following:

Pros:
Good command and morale to current troop
Strong units at game starts
Royal guards number regenerate

Cons:
Morale penalty when King die
King captured is going to be expensive (does anyone had your King captured yet ? How much do you have to pay ? Can you refuse payment to get rid of a bad King ?)
Can't train other generals

Thanks