Fair point, Would be nice to go one or the other at the very least, Compared to the M113's the ASLAV's will still be quite young once replaced, Would be nice to make some use out of the vehicle then scrapping it outright.
If you are going to go down that track, then it is probably best where possible to use a a common vehicle. Hence on one hand it may make sense to utilise the ASLAVs for such a capability, but if they are being replaced then means the Army thinks that they may be shagged so whilst you will have a relatively cheap upfront cost, the ongoing vehicle maintenance costs will be high as they increase in age. They will for all intents and purposes be orphan platforms.
OTOH, if you are able to use the same vehicle that you use as an APC then whilst the upfront cost is relatively expensive, the lifetime costs of the platform will be cheaper than the first option because vehicle costs are spread over a far wider base. My own view is that at present an 8x8 wheeled vehicle is idea because compared to tracked vehicles ongoing costs are low and if a wheel is knocked out it is easier to replace than a track, plus the fact the vehicle is not totally immobile until that wheel is repaired / replaced.
It's not as though you are going to take on a marauding Soviet tank army streaming through the Fulda Gap with something like these, because that's not what they are designed for. However, there are plenty of other scenarios on a battlefield where they can contribute very well. One is light amphibious forces as an example, especially in an airborne type operation well in the enemies hinterland. Since the ADF now have the C17s they would be able to mount such an operation using the C17, C130J, Chooks and MRHs. The US practices such ops.