I wanted to add my thoughts (partly based on XuaXua's excellent linked post). Some of this summarizes a few things people have already said.
It seems to me that there are 5 (or possibly even 6) scrolls for boosting weapons/armor:
- EW1
- EW2
- EW3
- Vorpal
- EA
- (Acquirement - some kinds)
These do 4 things, split rather unevenly:
- Increase the weapon bonus (EW1 EW2 EW3)
- Brand the weapon (Vorpal)
- Increase the armor bonus (EA)
- Change the armor type (EA)
I also included acquirement, because there are some parallels with changing a hide into armor... For example, if you acquire a weapon, you are most likely hoping for a better type of a weapon you already have (maybe you have a trident or falchion but want a bardiche or triple sword).
An easy suggestion would be to junk EW1 and EW2, just leave a proportionately more common EW3 scroll (call it just EW).
Possibly you could wrap EA and EW into an "Enchantment" scroll as those two concepts seem so similar. The obvious disadvantage is that this might hurt fighters who want to pump both armor and a weapon to high values, while making it too easy for other classes to max out their more limited equipment. However, I see nothing wrong with making something that's highly prized for one class and almost trash for another. Also it forces that hypothetical fighter to make some tough choices.
Now, off to the random thoughts section:
Vorpal does many things, which I like but, some of which do seem scummy or spoily to me. One suggestion could be to boost the "plain" vorpal brands, but not let you permanently apply other brands, and again to let it work the same for armor (+EV for robes or +AC for armors?)... Another alternative could be to give the player a promt to select the brand. I prefer the idea of asking "Which brand?" over having to learn a spell just to cast it once, vorpalize, then amnesia. Maybe you could also reduce the number of elemental staves, and have to produce those by branding a quaterstaff.
Then there's changing the base type. Again, I think the hide to armor trick is spoily. However I like the idea of 'earning' cool gear. On that note, a more radical idea could be to change how acquirement works! Make it more of a trade or upgrade than a totally free item. I suspect the effort involved in this is not worth considering.
Another suggestion that came up relates to making (or changing) artifacts or adding other powers (eg +Tele). Should these be manually applicable? I would say no. It sounds too hard to balance and overlaps with abilities from other sources too much.