I sure wish some accessory mfgr would put out some airline seats in 1:72, and cockpit seats for both 1:72 and 1:144. They could be pretty generic and still be okay- it would be a lot easier than scratchbuilding them all. Lots of the 1:72 kits have transparent windows, and most of the more recent 1:144 kits at least have transparent cockpit windows.
I did the Eduard civil Ju-52 about a year ago and bought the detail (PE) set for it. That was almost a bit overkill for 1:144, and cost more than the basic kit. Something a bit less would be fine- maybe just resin seats- by the dozen, maybe. They could be used as cockpit seats in 1:144. And it would be nice if the kit mfgs would at least include the cabin/cockpit bulkhead, and maybe even a cabin floor.