Thanks @Philosurfer for a wonderful contribution to this conversation.
I completely agree with you that there is a danger of idolizing the system of A-T philosophy, perhaps even more than the Bible and the Gospel message. There’s certainly many scenarios which could convince me, as a sympathizer of Thomism, to cease being an “orthodox” Thomist. Even though A-T philosophy, as an wide-ranging framework, is difficult to outright falsify, one can easily imagine situations where say, it makes things much less awkward to explain if we can allow a multiplicity of substantial forms in an object, as opposed to one form only (as @vjtorley alluded to). In fact, as a non-Catholic, I feel I am in a better position to pick and choose parts of A-T philosophy and theology instead of having to buy into all of it as some Catholics feel compelled to do, Thomas being an officially endorsed theologian of the church.
That being said, I think there’s a difference between discarding parts of A-T which are unhelpful, and completely doing away with all of scholastic thought, and eventually falling into heterodox theology. An example in this vein is the trend among some contemporary Christian philosophers (including Plantinga) to defend theistic personalism as opposed to classical theism: thinking of God as merely a super-powerful version of a human instead of the immutable, supremely simple Ground of all Being.
Now, there could be good philosophical reasons for a professional philosopher to reject classical theism. But I think there’s a difference between deliberately and knowingly rejecting something after having studied it (as Luther did) versus being taught by your pastor a theistic personalist view of God without even being aware of the historical, orthodox, classical view and thinking that it obviously must be the only way to think about God. Unfortunately I find that a lot of modern discourse about God and Christianity among the evangelical world is surprisingly historically naive - for example, it seems that we never know what happened, theologically speaking, between Augustine and Luther. Aquinas is either completely unknown, or condemned as “too Catholic”, even though classical theism was commonly accepted by both Catholic and Protestants for many centuries. An example in this forum: earlier, I mentioned the classical, orthodox idea of God as pure actuality and was met with an accusation that I was endorsing panentheism.
So to sum up, while one might legitimately conclude that nominalism is true, I think one should do so after considering all the options, and having obtained a good historical awareness of how things developed theologically.