Teaching Aramaic: Diachronic or Synchronic?

This note is more jottings for my own benefit --a form of thinking out loud -- than a fully considered proposal. Comments from scholars are welcome.

In teaching introductory Aramaic, the decision has to be made whether a synchronic or diachronic approach is to be used. The textbook I currently use (an unpublished text by another scholar) uses the synchronic approach, with the Aramaic of Targum Onkelos as the beginning dialect.

For a certain class of nouns, the synchronic approach leads to certain problems. Consider the two words gabra "man" and nahra "river." Although they are alike on the surface, a diachronic approach would discern historical etymons of a different shape, namely [gabr] and [nahar]. Because of differing processes of historical change, these forms have a similar outcome. Because of changes affecting monosyllablic nouns ending in a consonant cluster, [gabr] becames at a certain point [gabar] (with anaptyxis), and then [gbar] (with pretonic short vowel reduction in open syllables), although the base form for suffixes remains [gabr]. On the other hand, [nahar] was bisyllabic from the beginning, and only underwent the vowel reduction yielding [nhar] for the absolute, while the base form for suffixes also underwent vowel reduction, yielding [nahr-] out of [nahar].

But in the synchronic approach, is there any reason to posit different historical base forms? Can one come up with a set of rules that generates all the relevant forms, both absolute and determined, without appeal to historical forms?

Let's propose for both forms the underlying base forms [gabr, nahr]. The next rule would be:
A. CVCC bases must be changed to CVCVC in free-standing forms. This gives us [gabar, nahar]

Next rule:
B. Short vowels in open unstressed syllables reduce to shewa or zero. This gives us [gbar, nhar].

One could even reduce it to one rule, as follows:
A'. CVCC bases must be changed to CCVC in free-standing forms.

Does this work? Let's try it on two more nouns: sipra "book" and zimna "time."
A'. The rule rewrites [sipr, zimn] as [spar, zman]. These are the correct absolute forms.

But the rule should probably specify that the vowel in the rewritten form has to be /a/.
A''. CVCC bases must be changed to CCaC in free-standing forms.

Does this work? Let's try two more, malka "king" and laxma "bread." Application of A'' should yield [mlak, lxam]. However, these forms are not correct. The absolute forms are [málak, lxem]. Now what?

For malka, there has to be another rule modification, namely
A'''. CVCC bases must be changed to CCaC in free-standing forms, or else to CáCaC.

For laxma, the rule needs a further modification, namely
A'''''. CVCC bases must be changed to CCaC or CCeC or CáCaC in free-standing forms.

This rule might cover most forms. However, the rule has to be understood as predicting the parameters of possible lexical surface forms, and not as generating forms on its own.

I'm starting to think that the diachronic approach might just as well be introduced at this point. For instance, the diachronic approach will predict correctly that historical CVCC bases can become CáCaC or CCaC or CCeC, while historical CVCVC bases will become only CCaC or CCeC. This seems like a useful distinction to make.

Of course, this doesn't even start to deal with the question of spirantization. Maybe I'll deal with that in the next post.