I don't think the Premium package is required for the navigation system. I think all the B250e's are "navigation-ready" if you get the SD card for it, and that navigation is available if you want it separately. I think it's about $160 on Amazon, but you could whine a little with the dealer like I did. This might be the model that's needed, but check with your MB dealer:
https://www.amazon.com/Mercedes-Garmin-Pilot-Audio-2189063502/dp/B01N5UKJ8P
Installation was just sticking the SD card in and waiting about a minute to initialize.
Some other observations on differences between 2017 and 2014 models:
We noticed the missing nets right away too, and the trays.
The seat pans extend forward with a plastic pull to give a deeper seat
The rearview mirror is also on a thinner stalk.
The dials are more stylized though with lots more increments on the power and and speedometer and an extra ring of tick marks around every one of the dials. I like the detail.
The simulated ash wood on the dashboard that is included in virtually every B250e as an "option" is also nicer than the 2014.
The consumption/generation bar graph in the debut year is modified a bit to show the generation as a percentage of something - rather than the original unitless graph - showing recuperation is working somewhere between 0 and 100% of that motor's capability, I think.
Windshield defroster is standard as well the Range plus.
Right now, the 2017 CLA (and other MBs) shares most of the same features with an interior that is virtually identical except the RPM dial and Battery Power dials have different units, so I don't think MB did this especially targeting the B-class. Overall, it feels a little sharper with the small cosmetic changes and even may run a tad smoother and quieter to me but very similar to my old 2014.