By way of context, I am a phonologist, and I do not share your definition of the phoneme as a "meaning distinguishing segment", moreover I claim that socially speaking that the meaning definition is a view of phoneme not generally shared by phonologists, though it seems to shared by non-phonologists. I'm not pointing this out to harass you, I say this because it is an example of a view of theoretical concepts in linguistics that I think is mistaken. Specifically: the confusion between the definition of a concept, and empirical discoveries about the thing that the concept refers to. The "meaning-distinguishing" characterization is a far-removed theorem from something about what "phonemes" and other things are. If sounds X and Y don't happen to enter into a minimal pair in some language, that doesn't mean that they aren't distinct phonemes. The meaning thing is a potential consequence of something else, it is not the defining essence of "feature".
In that vein, then, there may be a "definition" of feature, but then there are empirical theories of the essential properties of features. Your question is not, as I see it, about the definition of features, it is a question about the nature of features in morphology. There is no reason to say that "feature" is a different concept in syntax, phonology or morphology, but these three kinds of feature may have somewhat different properties. "Feature" in grammar is one thing, and the relation "precedes" is a totally different thing – those concepts have totally different definitions.
The desideratum of avoiding syntax is highly problematic since most theories of morphological features are syntax-heavy (case, for example, can't sensibly be understood without reference to syntax).
In asking what the features of morphology are, the question apparently presupposes that there is a fixed list of available features, but that itself is a controversial assumption. For example, Ethiopian Semitic languages make a distinction at least between type A, B and C verbs, which plays a role in morphology. Bantu languages make distinctions in the tense system not just between completive and noncompletive, and past, present and future, they also distinguish a number of degrees of past and future, other distinctions such as aspectual focusing, "persistive", various expressions of speaker "attitude", not to mention clause type (main clause vs. subordinate, affirmative vs. negative). There are dozens of such verb forms as reflected in verb morphology.
There is a view of "feature" that simply says that there are "features", which are attributes, and the type that a particular feature has is language-specific. Given that perspective, there is no "list of features". Given a different perspective, one with a baked-in list of parameters (e.g. Optimality Theory), there probably has to be a fixed list.
