What are the negative implications for hosting on the same hosting account with a single provider in terms of SEO? I'm talking shared IP atm.
There are no problems with hosting different sites on the same hosting, unless you are planning to start aggressively interlinking the sites.
I wouldn't recommend this sort of strategy with any site you might shed a tear over if it was kicked out of the index. I've had a few sites kicked out of the index over my years trying to get an extra 10% or 20% boost in traffic and the pain of trying to get sites back in the index and the lost money in the mean time are just not worth it.
If you're producing junk throw away sites then designing a link network might be worth considering, but if you are just looking to rank in the Australian market, then 90% of the time some basic link building and onpage SEO will get the job done.
I don't know if this answers your question, but maybe you could give us a few more details about what exactly you plan to do.