Printers appear to be an unusual niche in that everyone needs them cheaply, but they also need to be highly precise to print documents and graphics well. So you have these cheap devices that pull off something very difficult -- thousands of tiny tiny droplets of ink per inch, precisely aligned, again and again, very quickly. But with plastic shells, mass-produced injection-moulded mechanics, and a few high cost, enclosed components.
This is why they tend to have no replaceable parts, and integrated print heads. Because user-replaceable parts mean human-level tolerances, not factory machine tolerances, and human-level tolerances mean badly calibrated prints.
In short, nobody wants to have to learn to tune their document printer the way everyone with a 3D printer expects to have to do.
There are a few things that your EPC printer could focus on -- standardised ink delivery, standardised print heads, modular linear rails. But it will be difficult because it is difficult to solve for all of those things cheaply.
If we could go back to e.g. the limitations of a golfball printer, we'd have ethical/open/modular implementations left, right and centre. Otherwise, be careful what you wish for, unless you really want to tinker with your printer.