Currently their are some rather odd non-material 'objects' in the game which the players puts in their inventory. Dreams are the first one the player encounters and I've described them as 'purple construction coupons' which is how most people treat them. Scents are the second and these are much more critical to the game as the whole justice system depends on them. Both 'mental' objects have a similar mechanic that if they are dropped on the ground they are instantly lost, yet they can be put in normal inventory containers which is quite impossible if we think about it for even a moment. Potjeh resent Ranger book thread made me think of how the games mental information representations are always forced into the physical inventory system because theirs no other option.
I propose that a player have a second separate inventory that represents the mind, it would be the same kind of 'grid' system but would have a different colored background to distinguish it (blue maybe) and mental objects can only be stored in this type of inventory. The size of said inventory would depend on Intelligence (not a 1:1 ratio of course but a series of row/column additions at particular Int scores perhaps maxing out at 12x12 at something like 1000 Int), this would help make intelligence not be a worthless waste of FEP. A generic 'book' created from parchment, string and leather would open up a 3x3 mental type inventory and objects their can be copied into the players mental inventory (if they can pass an Int check which could work like mining strength check "This idea is just slightly too hard for you to learn"), but the reverse (writing in the book) would require ink. It might also be possible for players to open up a kind of diablo style trade screen for mental objects ware they may present their objects for copying in the same manor but without need of paper (some kind of teaching skill could be used to make the learning players Int check easier).
Now under this basic framework for mental objects you can implement new type of mental objects and improve the handling of existing ones.
Scents no longer get put in crates and used by anyone, you could write them down in books though. Now of course I can hear you say "but that means infinite replication of the scent which destroys the system", which it would if not for the following changes, scents have a quality which declines over time and with each copying and usage. Thus the original Ranger will always have the best quality, anything he writes will be a bit inferior and the person reading it will get a yet more degraded copy (a direct transfer by window would be better). The lower quality will reduce the effectiveness of tracking in some way (I don't recommend simple radius based system like RR Extract) and when quality reaches Zero the scent is unusable.
Cartography could be made to work like our popular auto-mapping clients. A player with Cartography skill simply turns the skill 'On' (like turning on Tracking) and as they move around mental 'landscape' objects appear in their mind corresponding to each individual mini-map, it can be opened and viewed as well. They can then apply the landscapes to a piece of parchment (and expend some ink) and a map is created. An automatic compiling option would copy all their landscapes to available parchments (hour-glasses running back to back of course) at which point the player can clear their mind by dropping the landscapes to accommodate new ones. Now obviously people can and will still use automated mapping clients but this would at least be a competitive way to do it in game and the ability to exchange the maps in game should not be underestimated.
Dreams could actually behave like Dreams and be placed in the players mind inventory (if space is available) when they are logged off, but only after travel weariness is burned off. Many ideas have been suggested for how to make Dreams more usable but if their supply continues to come from objects made of sticks and strings they will never be valuable or believable.
Lastly their have been a lot of mentions of something called 'curiosities' by some people who apparently play tested a test server and can't resist hinting at this system, all I've heard is that is was some form of item based skill gain that replaced LP. Not knowing how it worked I can't really say if this is remotely compatible but I suspect it would be and could even be better implemented under these rules then under the current system of 'mixed' inventory.