STA bases his whole rational theology on his existence proofs, and all his existence proofs require him to assume the reality of the existence and operation of non-divine beings and actions (he even argues that the only possible existence proofs are one that assume the reality of non-divine actions and argue causally to deus.)
This means STA has to logically rule out many well-known theologies from the beginning. Obviously Eastern or quasi-Eastern nihilist theologies are ruled out, but they were probably never much of a temptation to the sorts of persons who are attracted to rational theology. More significantly, a Thomistic occasionalism (whether the Islamic or early modern version) is a logical impossibility since denying reality to non-divine action would, for STA, make rational theology impossible. But most significantly, no Thomistic account of divine premotion or the predestination of the saints can be read as a denial of the integrity and independence* of non-divine action since to do so undermines the ultimate basis of any account of premotion or predestination of the saints.
One objection to this is that a “natural” action would be no less real if it were utterly dependent or to some extend independent. We might very well start off assuming something is non-divine and then come to understand ourselves as mistaken. But I think that this underestimates the role that existence and operation of the sensible and finite plays in the existence proofs. STA has to rule out any eliminativist or strong reductionist accounts of creaturely existence and action, since to do so eliminates the only explanadum for which God is rationally necessary.
*Independence comes in degrees, but Thomism can never understand “what’s really going on” as the propagation of a divine action through inert and utterly dependent created instruments. For STA, the idea that “our merits are only God crowning his own works in us” can never have a rational foundation.