Ammo logistics is an art as well as a science regardless if your guns operate in clumps or individually. Caching presupposes some form of stability - possible for defensive and retrograde operations (albeit one might have to BIP a few) while in offensive operations your caches need wheels under them. I don't want to sound too negative but in 2006 we had trouble getting it done right for as few as four howitzers.
Again, easier said than done. We have much more capable computer systems now that can work all of that out on the fly. Dispersed guns can mass fire much easier now then ever before. Precision munitions require far fewer rounds to achieve effects but providing them with security and sustainment is significantly more complex. One complication is that gunfire attracts counterfire. Rear area space is at a premium. One doesn't want their highly mobile guns to shoot and scoot from next to some other installation that isn't as mobile and parked in the same space. Guns, especially close support ones, aren't as free-roaming .
Not really a "lot" of trust. It's a capability for some guns and runs more as a marketing feature rather than a true practical feature. We've played with this concept since the 70s. MRSI only matters for targets that can rapidly change their profile, like troops in the open, who can go prone in an instant. With variable airburst ammunition that doesn't matter as a prone person makes at least as efficient and airburst target than a standing one. Targets that can leave the target area, like armoured vehicles, are more complex and with those one guided munition far exceeds the effect of a number of MSRI delivered dumb ones. (And I don't think we have the tech available to easily guide multiple MSRI projectiles)
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There very definitely are. But you have to keep thinking in layers and capabilities and desired effects and how to employ the different systems efficiently and economically. One tends to forget that economy of effort continues to be a principle of war. You can't keep throwing $100,000 and $1,000,000 missiles and rockets at everything. Sometimes a $300 brick of steel and TNT will do. Canada has an issue with scale as well. And as I keep saying, until you find out what we intend to do as a country, all speculation about the tools needed are just that, speculation.