Right, a couple of things....
- Austronesian vs Philippine - what conlangers typically talk of as "Austronesian alignment" is actually more precisely known as Philippine-type alignment. Philippine alignment, as the name suggests, is found primarily in the Philippines, and some parts of northern Indonesia - and I think some Formosan languages, and arguably Malagasy. The core of Philippine aligment is that there are multiple non-agent voices (or 'focuses') - originally probably three - patient, location, and instrumental/benefactive. Some people add arbitrary additional restrictions to exclude languages like Malagasy.
But most Austronesian languages don't work that way. In particular, many Austronesian languages are (morphologically and syntactically) 'symmetric voice' languages, like Philippine languages, but, like Telpahke, have only two such voices, rather than four or more. Telpahke is thus, in this regard, broadly speaking an 'Indonesian-type' symmetric voice language.
- the really weird thing in my opinion is actually the genitive. In Austronesian, and I believe worldwide, it's very common for the ergative (Case 3) to also be used as a genitive. You instead use the accusative (Case 2) as a genitive, which to me seems really... odd. Is there a particularly reason for this? [is it perhaps a relic of the accusative being used after prepositions, and the preposition of possession has just dropped out somehow?] Is it something to do with a partitive, maybe?
- your "prominent argument" also seems strange to me - you use "topic-like" as a synonym, but in your examples you appear to instead be identifying it with focus, not topic. The topic is old information, not emphasised new information.
For instance, in Austronesian it's common to have a rule saying that only definite nouns can be the subject. This makes sense if you treat the 'subject' as topic-like - topics naturally have to be definite (or something similar), and definite nouns are already somewhat topic-like. But in you example of the answer to "what the hell is the woman cooking?", there's no need for the answer to be definite. Often, it won't be - what the hell is she cooking? Fish is what she's cooking. 'Fish' here is not a topic, and in Austronesian alignments it can't be the subject, but in Telpahke it can be. (Notice that in English, it's more natural to keep 'fish' as the object there (fish is what she's cooking) than to promote it to subject through passivisation (fish is being cooked, fish is what's being cooked) - again because it's a focus, not a topic).
[A question that would provoke a topical 'fish' would be something like "Tell me about the fish?" or "What's happening with the fish" (answer: "It's being cooked (by the woman)" - promoted to subject in English precisely because it's the topic). ]
At least, so I understand it. I don't natively speak a topic-prominent language myself. But it does look like yours is focus-prominent instead, which is indeed very unusual. (does it ever happen?)
[Austronesianists sometimes use "focus" to mean "voice", but that's unrelated]
- split-intransitive: natural enough in Austronesian. People seem reluctant to discuss it openly (because the transitive alignment is much more exciting), but I get the impression that it's not uncommon - transitivity being such a big issue in the family. Himmelmann gives the example of Balinese, which splits its intransitives through voice marking on the verb much like its transitives (with the exception that one of the voices on intransitives doesn't appear on transitives), and of Acehnese, which apparently deals with voice on intransitives exactly as with transitives, and specifically splits its intransitives by the level of control (though the marking is done by having obligatory verbal pre-clitics with agent-like intransitives, and optional post-clitics with patient-like intransitives).
[my own Rawàng Ata, incidentally, works like this fundamentally, though there are also complications]
- have you given any thought to how you will handle dyadic intransitives? Are they like normal transitives, or perhaps like passive intransitives? Are you sure all your 'transitives' are actually transitive (because that could motivated voice changes)? Or are some of your intransitives actually transitives with elided arguments?
But the river tripped on her by and by, lapping
as though her heart was brook: Why, why, why! Weh, O weh
I'se so silly to be flowing but I no canna stay!