With respect to casing design, that only takes approx. 3 days, the inclusion of space for PSUs has been passed on and acknowledged, and is being considered. Such design does obviously affect shipping costs that are dictated by dimensional sizing and weight, but you will need to source PSUs your side. This is not an oversight on our part, but the regulations for importing products with power supplies varies significantly country to country to the extent by which entry of electronic goods that have not met the prior approval of specific countries. If you have been on this forum long enough you would be well aware of the complications and denial that some have experienced, as such we will not provide an internal PSU so as not to limit access to those customers. Keep it simple and ensure everyone has a fair chance of receiving their items. Power supplies are easily available internally anyway. It worked well for Jupiter so we're sticking to that.
My understanding of the neptune was that it was going to draw 2500w or more, and thus is unsuitable for 20 amp, 120v power lines. I'm not sure where to get a power supply that is greater than 1600w, and I've always been cautious of having two power supplies on one device, in case one fails and the other does not. (electronic devices don't generally like to be half powered... it fries them!) How would sourcing your own power supply work with such a device?
+1 for the suggestion to house the power supply internally. I (and I am sure many others in the US) plan on hosting this in a data center, so having it something that is entirely rack mountable makes things so much easier.
I think it's easier for all of us 
