...this is the problem, the old reputation value to our knowledge cannot be removed from information window.
Well, heck, if that's the only problem, I'd be willing to accept having a meaningless variable in my Records screen in exchange for meaningful Falling any day. Just call the new Rep variable "Esteem" or something like that, and display all 3.
Well, you'd want to change it to a middle value (say, 10) and then modify happy.2da to prevent everyone from spouting lines about your current reputation. They'd then have to be scripted, but that's perfectly possible (but unless some extremely clever code is come up with, it wouldn't happen by default for mod NPCs). In fact you'd want them scripted to be responding to your Virtue really.
Could it be an optional component to Virtue to stop Paladins (and Rangers) falling? (some people would want to roleplay evil)
Were this kind of idea implemented, there's no reason why not, but it's up to Sim.