More importantly, it is no more necessarily violent or terroristic than, say, Christian Dominionism is (that being the closest analog I could think of).

Then isn't a problem with using the term "Islamism" to refer to atrocious, violent terrorism that one will by doing so discredit whatever non-violent Islamist movement may exist? Or is that your intention?

(Personally, given the obnoxiousness of shari'a to anyone who isn't a male Muslim of public piety, I have little problem with discrediting peaceful Islamism as well).