I am constantly frustrated by the lack of support for the IPN format. One suggestion I have to improve it is as follows:
The current IPN environment has no easy way to keep related groups of parts together while exploding. Often in exploded views you have a set of components that are tied to each other in some way (maybe a press-fit pin or a bearing bolted to a machined plate) and you want to keep them together. The most common example is a shaft assembly. An assembly will contain a shaft which is connected to a housing somehow, this shaft may have gears, sprockets, spacers, bearings, cams, keys, and many other components that all slide onto the shaft from the end. The best way to show this in an exploded view is to have ONE TRAIL (Inventor is really bad about having a million and half trails and segments) connecting the shaft to the housing and then have all of the shaft components exploded in a straight line off of the shaft with the trails in line with the centerline of the shaft. Currently the only way to do this is to select the shaft and each component on the shaft individually (*cough* window select *cough* http://forums.autodesk.com/t5/Inventor-IdeaStation/Window-Select-in-Presentations/idi-p/3684114). After doing that you tweak the group to the point where you want the shaft to be then tweak each component until they're all in position. At this point there are WAY too many trails in the way so you have to hide each trail manually.
I'm not 100% sure what this fix/feature would look like but there are a couple of things that I know need to change:
1) Subassemblies shouldn't be broken up. If I put components into a subassembly, I WANT THEM TO STAY THERE (even in an explosion). I think you should have to right-click and have an option to break apart subassemblies if you happen to need one broken down.
2) When you tweak multiple components at once Inventor should only place one trail (at a custom location, http://forums.autodesk.com/t5/Inventor-IdeaStation/Bring-the-presentation-environment-up-to-speed/id...).
