The biggest problem with HIGNFY is the guest presenter ploy. The second biggest problem is that they think Alexander Armstrong would be the best permanent replacement.
With guest hosts, as we saw through half of this week's episode, they end up wasting an awful lot of time with gags relating to that host and their particular schtick. Alright, so they may often be quite funny in themselves, but it hardly creates a great atmosphere for biting satire, or keeping guests and regulars on their toes.
If HIGNFY has even the slightest delusion of being satirical - and Moore's reading out of the "Ian will explain" cue this week shows that it does - the format desperately, desperately needs a single, regular host who can offer consistency, reliability, and frankly just cut through the cheap host-based gags. They may be funny, but cumulatively they simply serve to detract from the satire.