Excellent post JS. Basically agree with all you say but have the following comments.
1. My immediate reaction would be we can't afford to sack him but, as Finchey says, "What is the more costly?" Interesting question; unfortunately I couldn't even hazard a guess.
2. Sure Scotty as manager would be a risk. But, isn't that how we started with MON? I don't think he came with qualifications of any note as a manager. Personally I'm not one to be impressed by CVs and qualifications, things that can be made to look better than they are. We've had some right ******s come here with supposedly glowing CVS. Much more interested in aptitude for the job, passion, drive, ability to motivate and, with our budget, would rather risk someone with these qualities (at a price we can afford) than (say) someone who has managed to get a job with a team from a higher division. Alan Smith and John Gregory spring to mind.
I'm not sure that we can be confident of staying up this season to be honest. If things continue to deteriorate then maybe some calculations should be at the ready in order to assess the feasibilty of the sacking option.
We were mostly happy to drop down to NL status rather that carry on under Hayes so, in some respects, we should be happy we are where we are and just hope we can stay up under Waddock and review the situation when his contract expires.
I wouldn't make any rash decisions just yet but if it could be shown that turning to a lesser experienced, dedicated manager (eg Scott, Brown) could be financially advantageous, maybe this is an option for further consideration between now and Christmas.