Regarding RAM, with laptops, you're often restricted by what the chipset will actually support, and that's the case for MBPs (still 16 GB as far as I know). Soldering or no soldering, that's the real problem.

The actual bitch is soldered battery. Mine (2012 MBPr) is still giving me two to three hours, depending on workload (and sticking to Safari for browsing, which makes a massive difference in power consumption), but a replacement would make me more comfortable. I can't imagine what Apple would make me pay for that.

A secondary annoyance is the proprietary SSD interface, which dramatically restricts the choice of hd vendors (for my model, I think the total number of vendors is still 1; I believe a couple of other vendors do support more recent models). I currently live in fear of this disk giving up the ghost before Apple will actually release a new MBP worth buying.