RC delegations potential non-consensus issue (test scenarios)

Question is: can malicious witness exploit RC delegation?
i.e.
(a) alice fakes delegation of huge amount of RC (that bob has) from bob to alice.
(b) alice fakes delegation of huge amount of RC (that bob even hasn't) from bob to alice.
(c) valid key is used but amount is way over available balance.
etc.

Neither would be accepted by a honest witness, but it takes only one round of block production when alice is scheduled to produce, to generate and self-accept such non-consensus custom json transaction.