What sorts of problems? I didn't really change anything in the artifact rules, just in how the end up presenting themselves in the game.
Well, your first solution - the regular magic staff that blossoms into an artifact near the end of the game - is balanced but pointless. The whole idea is to have the Staff of Magius be Raistlin's signature item. If it spends the first 5/6 of the game being just another boring magic staff, Raistlin has no motivation to stick with it. Even if he knows it's going to turn into an artifact, he'll just shove it in his
bag of holding till late epic tier rolls around (if it ever does), and use the latest magic staff he found on an adventure in the meantime.
Your second solution - the artifact that "rolls over" and is replaced immediately by another artifact when it moves on - is CRAZY broken. The single balancing factor on artifacts is that they
do move on. You don't get to have them for more than a couple levels, so they don't have a long-term impact. If the artifact is instantly replaced by another artifact every time, then that one balancing factor is removed and the Staff of Magius becomes ludicrously powerful.
No, not to cram anything into anything else. It's you have the basics for something that's built with the idea of balance, but you want to modify to fit your vision.
But the thing that's built with the idea of balance (artifacts) is wildly different from my vision. Modifying it to fit my vision requires so many changes that by the time I'm done, I can't count on that built-in balance working any more, so why bother?
But the point is once they DO stat up that stuff like that as a new class of item, it falls into the category of "Items people now expect WoTC to find the magical balance for" and "items players expect to see at some point because they're in a published book," instead of just being a cool new unique thing the DM threw into his campaign.
Pfft. When WotC released the Tome of Magic in 3.5E, did everyone suddenly expect to see incarnum users in everything? This would be a non-core supplement (the horror!), and traditionally stuff from non-core supplements
doesn't show up in other published material, because you don't want to limit the audience for your latest adventure to folks who have the Minor Artifacts Handbook.
I suppose such a book would conflict with WotC's "everything is core" approach, but frankly I think that approach is silly and potentially destructive to the diversity of the game. There's room out there for more than one playstyle.
(Of course, those playstyles could be supported by 3PPs, but WotC more or less killed 3PP support for 4E with the GSL fiasco, so... yeah.)
I just don't personally see the need for a new rule when I already have what WoTC considers to be the optimally balanced idea for magic items. I can adjust from there as I see fit. I don't need a new rebalanced rule for every variation someone can think of.
WotC has rules for low-powered items and rules for artifacts. Neither does what I need done. That being the case, I homebrew, but I'd certainly like rules support from the pros and I'd be willing to shell out some money for it. Other people here seem to feel the same way. If enough people feel that way, we've got ourselves an untapped market.
If WotC doesn't feel that market is big enough to make a Minor Artifacts Handbook profitable, so be it; but their stated reasons for "why we can't publish this type of item" are silly. If you don't want the MAH, nobody's going to make you buy it.