Would paying voters object to such a decision?
Some definitely would, but the important point is that C5 would be in breach of Ofcom rules if they tried it.
Ofcom tightened-up the rules a few years back, and broadcasters must announce the exact nature of the voting before the lines open - and then stick to it.
I'm not 100% certain about midweek evictions during the final vote-to-win, but from memory, BB has only once changed a standard eviction after voting started: that was in BB7 the week that Mikey and Susie went in a double. When nominations were announced at the end of the evening's HL show, it appeared to be a normal (single) eviction, but the next day the ads had been changed to state it was a double eviction. No reason or even acknowledgement was given, and it's possible that they forgot to announce a double from the start, but it looked suspiciously as if BB changed their minds because they realized Susie wouldn't go in a single eviction. Either way, C4 got into a lot of trouble over that (although it was all rather overshadowed by the "returning HMs" fiasco).
Bottom line: if this Friday's eviction is suddenly changed into a double (or more), C5 will be reported to Ofcom. Whether C5 (i.e. Richard Desmond) actually cares about that is another question entirely...