Well, after further consideration I have to temper myself here a little. This is, after all just going to be a hobby. I have no intentions or desire to do this professionally (I've already fallen into the "turn your hobby into a job" trap before and don't want to do that again).
So, in that line of thought AEB isn't a big deal. If I'm too lazy to manually make three exposures and set the EV then I'm just too lazy. As I found after more reading last night there are any number of tethered or even a wireless option to do AEB later on if I so choose.
The availability of older (i.e. cheaper) lenses has grabbed my attention. I had already "assumed" that any new lens was going to be a major $$$ investment and that to some degree was partially responsible for my desire to have an MP-E65 (and subsequently another pricey device in a decent flash set up, such as the MT-24).
I think I can probably assemble a nice macro set up that will satisfy me and not break the bank either. It's pretty clear that I'm not going to achieve some of the results I see without a pretty hefty investment (and assuming I can develop the skills to go with it), so for now I'm willing to accept less for less. Then there's always hope Nikon might come out with their own 5:1 lens one day...
Either way, I think for my budget (and future budget) Nikon is the way to go and the D3200 will do me quite nicely. It'll certainly be capable of far more than I am at this point.
If for some reason later I find myself in a financial situation where the cost of cameras and gear are less of an issue, I can always trade up to something bigger and better, or maybe even just buy a Canon and that MP-E65. At this point I either go entry level and work with it, or I don't get a camera at all. I'd rather have the entry level camera and less than uber, stellar lenses and at least be taking photos than not to have one at all.