Granular / threshold based co-signing

To improve adoption and security of NEM would it be possible to introduce co-signing by default? At the same time allow a threshold to be set with granular control, e.g. co-signing is needed above a certain level (equivalent of  say $10) but below this level to ease usage no co-signing is required?

KC

I think some people will want it and others not.  I use it personally