The thing is that we have no idea how much the battery life would be affected by the DDR4. I'm sure Apple tested models with DDR4 (going back to when they switched the MBP to LPDDR), and found the battery life to be completely unsatisfactory. This is what I'm most concerned about, is that we have no clue whether DDR4 would impact the battery life slightly, or majorly.Other than doing 32 GB of RAM the same way HP, Dell and Lenovo workstation notebooks do (by sacrificing some battery life and using DDR4), the really interesting upgrades don't exist yet. If I were Apple, I WOULD sacrifice the bit of battery life and offer the extra RAM on the 15" (only). I'd also leave a couple of legacy ports around (1 or 2 standard USB, the SD reader and perhaps HDMI) in addition to the USB 3.1 ports...
Ports, I haven't really had a problem with them, but there are plenty of people who have. The very least Apple could've done is "generously" include a USB-C to USB-A adapter (like they do with the iPhone and the 3.5 Jack) Not including an SD card reader when SD cards are the de facto standard for cameras seems really obtuse though (but they're also pushing the iPhone as a camera replacement, so maybe that's the logic).