One case that can pretty much do it all in the mid-power range (E-G) is the AeroTech 29/40-120. I have only used mine for G64s but there are a total of 8 different reloads that are compatible with that casing. Biggest downside to this RMS is that the closures can only be used with that casing.
A runner-up to that would be a 29/60-100 system (either AT or Dr Rocket). Big difference there is that you get 2 casings (a 60ns & 100ns) with one set of closures. Biggest advantage to that system is that the closures work with the remainder of the 29mm casings (180, 240, & 300). However, it seems like the reloads for the 60 & 100 casings are harder to find. YMMV...
Only other choice is the Pro38 1 grain. While undoubtedly the easiest of the bunch to use, it is far & away the most expensive at ~$20 per reload. Other downsides include only 2 different propellants available (classic & Smokey Sam) & those reloads are "only" G motors. And Pro38 motors (regardless of size) always ignite soooo easily!
HTH,