DO note before reading, I never owned one of these things, of any revision. I am just working off of prior knowledge elsewhere, hardware already available and an idea on how I'd like to build a cheap PC, and whether or not it could be feasible.
I want this thing to have an optical drive and hard disk. So using the RPI3B as a base, and assuming my hardware is intended for laptops, without going into details on how in my head I want to mount this stuff I want the data and power to be done as easily as possible. The easiest way I can think of is as such;
SATAd -> USB
SATAp -> LP4 / Molex
Using the power demands from the ModMyPi website, they claim all you need is 5V@2A to run the Pi. Whether this is true for the 3B is something I am unaware of, but i am assuming this for the hell of it. It still needs power, and 5V@2A is easy to come across yeah? Every power brick for LP4 has both a 12V and 5V rail with 2A. So then I wonder;
If I were to chop a USB B Micro dedicated charge cable and crimp on (or solder in) some pins and shoved the ends into an LP4 housing, could I then power the hard disk, optical drive and Pi itself using a 1-to-3 LP4 adapter with the receiving end outside of the case?
The thing has a CSI so I could add in a camera which works with the B3's interface and have that somewhere, or I could just run it from USB by having a USB pass-through on the outside of the case, or separately -powered USB hub if I wanted more equipment. Wireless could be handled by a USB-connected Tx / Rx and the media devices could be plugged in via USB by a SATA to USB adapter.
I read earlier that you can boot from USB with some tinkering about, so would it be possible to use a 256KB microSD and use that to put the bootloader on, which could then be used to boot off the hard disk?
Would it be too much for some cheap LP4 power adapter to handle? Would I need additional components? I already know I would need to extend the HDMI connector to whatever case I shove it in for video. I'm just poking here so don't bite back too hard, please.