The Octane renderer does not natively provide this functionality, so it would need to be done at the plugin end. The only plugin that I am aware of which implements this is the DAZStudio plugin, and IMO it works out to be very confusing to the user, and is not something that I think is of sufficient benefit to justify the downsides.
Professional maps are in super hi resolution...so sometimes I need these maps as they are...other times I have to downsize because projects with many super hi res maps are too much for the vram. So every maps have Diffuse map, bump map, reflective map and so on. It is really annoyng to downsize in photoshop dozens of maps. IMHO it would be very useful to have a parameter (in percentage and for every texture slot) that allow to load maps in a "light version". I would save a lot of time.