Add to the OP:
Trying this rule out:
That being said we need a time frame that the challenge winner has to post a new one and if they don't we need a statement of what happens next.
IMO it should be 24 hours starting Monday's at 8am through Friday at 8pm. Anything posted between Friday at 8pm and Monday at 8am has 48 hours to reply.
If the challenge winner fails to reply within 24 hours during the week and 48 on the weekend the previous challenger will then post a new challenge to keep the game moving and the challenge winner who failed to post within the time frame will be deducted a point.
Also, why only 'till April 1st?
Number 4, OP.