there is space for ram on the back side. don't need to remove the discrete graphic.
quoting apple, the lack of 32gb option at this time is due to battery life. presumably the next gen 15" will have more efficient processor and ram, and larger battery, thereby allowing the additional ram spaces to be used.
what a mess inside. especially given the spaces around the batteries, and the off position of speakers, looks like the chassis was optimised for the non-touchbar version (much cleaner layout, removable SSD, no gaps), and touchbar addition was a later decision. Maybe initially they envisaged only the 15" would have touchbar.
a similar case of "odd unused chassis space" happened with the first gen 13" retina macbook pro, which had empty space under the trackpad. Was probably a late decision to use small form SSD over 2.5" SSD. this empty space was used up on subsequent updates.
to me the touchbar version has way too many compromises. the biggest issues are: smaller battery, while using a processor with a higher TDP. and non upgradable SSD (arguably the only component that might require future upgrade, unless you want to pay extraordinary money right now).
