.the six i mentioned seemed to me to be the most unrecast-able for the reason you mention.audiences wouldn't except it.
I love Louis Edmonds as Roger, and all of the other characters he played. He played the arrogant snob to perfection. Nobody could have done as good a job, definitely could not be recast.
as barnabas' bride pointed out any attempt to replace him would have crashed and burned.the audience simply wouldn't have been accepting of anyone other than frid in that part.
it's impossible for us to know today what would really have happened should frid have decided to exit the show but i think that abc would have really had no choice but to cancel it.
Actually that's not true, we DO know. Frid's contract ran out sometime during the 1840 plotline and he only agreed to stay with the show if another, non-vampiric character was created for him, hence Bramwell Collins in Parallel Time. Well, we all know what happened after this plotline.
And as we know, the ratings actually went up during 1841PT