A most interesting post. Almost sounds like Lady Catherine was describing Charlotte !
I think Mr Collins over-inflated sense of self-worth made him sure of success with his proposal to Lizzy.
Perhaps it is an amusing subtlety by JA , that Charlotte proves the ideal wife for him. ;)
Charlotte has no delusions of Mr Collins' charecter but hopes for security and a measure of material comfort.
Mr Collins is servile in praise of Lady Catherine, yet I think perceives little distinction between his patron's possessions and her advice.