Between running test scrips for Damage Field we're working on the ESP rules. We now have a taxonomy of kinds of ESP and individual abilities. It's a Google document so I might have a way to share it with people who are interested.
We are considering a few key points.
Our observation is that players will want to do things to improve their SP-count (such as getting an object that was cherished by the subject they are trying to ask questions about) but there will also tend to be some quick-hit "let me see what I can get" types of uses. We want to sort of support a model that gives the character a shot at whatever they want to ask but then allows them, if it's not satisfactory, to try for a better read. We're thinking of this right now as a "free" use and then a "more detailed one."
The real problem is that we don't want players to just be able to hammer away at whatever question they have until they get the good roll. This will cheapen the system dramatically and will necessitate a lot of rules about how long you can keep trying and what constitutes "the same question."
One of our thoughts is that PCs might have a pool of SPs that recharge every game session. They can try a roll without using them but the odds are lower. If they engage them they have to beat the number of SPs they've already used in order to try again (the GM determines what the same subject is). More over, this will allow the PCs to determine when (during a game session) they really want to go for broke vs. just attempting things.
The thought right now is to allow them to spend one SP from the pool for each SP they can get through other means.
The taxonomy of ESP stuff is not /that/ different from what we had before but it's far more encompassing and I've gotten about half way through defining a per-effect-level result for each one which should make using these far less generic.