A) WTF does factored mean?
B) Maintainability? See A!
Typical users aren't programmers and don't give a flying patootie about factoring, maintainability or fragility. And rightly so. The financial analyst getting that report to the CFOs office in 1/2 and hour had damn well better know finance - and enough about the tools they use to get the job done. If it needs to be better than that, then it needs to get properly built and the company needs to step up to the plate and make that investment.