OK...there's a pretty critical mistake in this build. And to examine it, let's look at the ACTUAL costs for the Neutron and Pico III in this particular configuration...figures in USD, but the point should be obvious...
To house the Neutron at 70 hp in a case where each 1 hp space retails at about $2.25 will cost you around $156 ADDED to the price of the Neutron. And the Pico III, while it does come in a Eurorack version, probably makes more sense as its standalone version given the tight panel space and the Buchla Easel-type cardslot...but if this was that version, it would cost an extra $98 to rehouse and repower it. And all of this is because these synths (unless the Erica is the Euro module version) already have cases and power, ergo you're doing this TWICE...and paying for it twice, too! It might be convenient, it might be space-efficient...but there IS that hidden cost in there if you decide on that course of action.