If some of them are wildly inaccurate representations of the interior of the building, my inclination would be to delete those outright.

We do tag footpaths and corridors through railway stations and shopping malls, often as highway=corridor or highway=footway + indoor=yes. I realise that in those cases, they're more useful to routers as they are usually places which you can go through rather than to.

Using indoor=footway as a replacement for highway=* seems somewhat unsatisfactory. Not only is it undocumented and likely to be ignored by data consumers, but the simple indoor tagging scheme is based on area routing and indoor=footway might be expected to be a polygon rather than a line.
https://wiki.openstreetmap.org/wiki/Guidelines_for_pedestrian_navigation#Inside_buildings

Maybe it is worth keeping some of the land side footways/corridors between the pedestrian and public transport entrances, connecting with the lifts and escalators? These seem to me like fairly sane and useful endpoints for pedestrian navigation.