Just to babble a bit, I've no idea how to package this thing- other people here are way better at that. Standards are nice, but can make the physical hardware costs very high. I remember Eurocards, with high pin count on the connectors, but also high backplane costs. There are "NIM bins", Nuclear Instrument Modules, but I don't remember much about that format, only that it was reasonably narrow. No doubt there are many other modular standards. Or, you can put everything in a single box. With a single PCB and all connectors on that single PCB, costs would probably be lowest.
I imagine the basic functions to be 3 major user blocks. First you have a DVM module. Next you have another DVM module that can also be set up to measure current. Third, you have a source (synthesizer signal generator) module. So maybe the box has 3 sets of leads- bananas, BNCs or whatever. So far, pretty simple and just an enhanced DVM.
The key is that the input modules are all fast ADC, feeding a "brain" (either internal CPU or external PC) instantaneous data. Now, with voltage and current, you easily get DC power- that's a no brainer. But it doesn't work for AC. However, if you do instantaneous voltage and current, that does work for AC. So now you have a proper (and high $$ value to the customer) VAW (volt-amp-watt) meter.
Add the signal source, plus the ability to measure instantaneous voltage and current, and you complete the picture, being able to excite the DUT (device under test) and measure its transfer function and impedance at any frequency. IMO, the instrument should work from DC to about 1MHz to be useful.
Hopefully that defines/explains things a bit better.