for backwards compatibility, with any client that doesn't mention it knows about the system and wants control, the server applies the constraints and forces and control responses that match the current system but for clients that does confirm to the server it knows about it and wanna do it, and for scripts (perhaps only with permission from the user, perhaps auto-granted for attachments), every type of constraint and forces, as well as separated sets of those properties for varied conditions (including control inputs, collisions, position etc) would be handed and opened for re-writing this should allow for different handling of jumps, client-controlled flight assists, turning avatars by script! Changing the "up" direction of avatars, buoyancy on water and much more. And recreating the default behaviors under the new system will likely fix things like those jammings that happen when somthings at different stages of jumping go wrong and keep the avatar locked with some unwelcome constraints The conditional changing of constraints and forces might require some sort of programming/scripting language of it's own to allow flexible customization, the ability of making things analogous to that the ceiling for flight, locking controls on hard landings for a few moments, allow time for animation before actually lifting off jumping, that stickyness to moving phys platforms I saw some Linden talking about elsewhere etc. Clients have the issue of network lag, and scripts can't perform fast enough for these things without overloading the sim, clients and scripts would simply instruct the server how to act on each situation in place of the current default behavior. If there is concern about leaving the avatar in an unwelcome state when an attachment is detached, or an object gets out of range, give a button like Release controls for restoring default settings, and an option like Stop All Animations that also restores the default behaviors for cases where there isn't anything to be released anymore, and also make it so that changes caused by an attachment are reverted when detaching (except perhaps if a permission is given by the user, this one can't be auto-granted for attachments, and this permission for persistent changes should also be requested by non-attached objects (regardless of owner), some multisim environments might want to have everyone moving under different rules seamlessly) Actually, it would be interesting to have sims have their own defaults, that can be overridden by parcel options, as well as client/script direct manipulation, perhaps have a preference in the client about automaticly accepting, always asking, or never accepting the defaults of the land. Perhaps even make the individual sets of constraints and forces for each condition be a new inventory type, with all the permission stuff, but kinda like animations, allow inventory items that are restricted to the current owner be "played" on anyone, a no-mod, no-copy behavior set could be put by the sim owner into the sim settings, for a single sim since it is no copy, and without the sim owner nor any users seeing the code behind it, it would work for everyone in the whole sim. People could "wear" new motion behavior sets directly from inventory. This could be the origin of a whole new industry while at the same time easing the load on sims caused by flight assists, jump enhancers, "dashers" and many other lsl attempts of modifying the motion behavior of the avatar