I agree with your opinion - if you want to be the champion, beat the champion !! On the other hand, I don't like your last idea of two champions. The way the champion is determined right now is exactly the combination of those two. You beat the best tournament players in the tournament and then you beat the best match player in the match. The champion is absolutely worthy, no matter who is him.
Imagine something similar in tennis - 5 games Djokovic - Nadal in one week ? Or in football Brasil - Spain best to 4 wins..
Magnus Carlsen has gone on record as preferring a tournament to decide the World Championship in which the reigning WC must also play . He thinks the WC should enjoy no special considerations and be seeded into a match for the WC once the chalenger is determined . Will he change his mind if he becomes champion ? Time will tell .... I for one completely oppose such a change and believe if you want to be the champ you must beat the champ head to head ... in a match ! Someone like Petrosian would likely never have been champion under a tournament format as he drew too much but rarely lost , which is great in a match but not a tournament . Geller probably would have benefitted from a tournament to determine the champion as he was much better in tournaments than in matches . Maybe there should be 2 world champions ? A champion of tournament play and a champion of match play ?