I have to admit that magic is a bit of a mess. I've been looking over the spells and see a lot of fixing needed. Years ago I made a couple passes through the original Microlite and d20 System Resource Document (SRD) spell lists in order to make things work better with HP based casting, but there is still a lot of spells that are either duplicates or sub-par versions of other spells. There'e also spells that are too weak or powerful for their level/cost, like Fly is the same level as Illusory Script for example. I don't take all the blame for this since the source material is pretty wonky as well and some of those old D&D spells are unbalanced with some just not great and others are too good. That approach can work if you have to pick X spells every morning, but not when you can cast any spells you know if you have enough zap left.
In any case a lot of spells have suffered in translation. I've been whittling away at fixing these again. I'll give some examples; Magic Missile is a first level mage spell and so costs 3 points to cast for 5-8 damage, and you have to roll for it. In game terms this means its about as good as one sword hit but with a HP cost and I can;t see myself using that spell over a dagger if I was playing a mage. I think it might work better as a level 0 spell costing 1 hp and doing 1d4 damage. It's more likely to be used at the lower level BUT at the same time its not going to be like 5th edition 'eldritch bolt' kind of laser blast because it does take 1 HP to cast. A 3rd or 4th level mage is still going to rip a few of these off now I think.
I'm also looking for spell 'overlaps' to fix, consider the Enchanter spells Stinking Cloud (lvl 3) vs Rainbow Pattern (lvl4). These are essentially the same thing but Stinking Cloud is probably better mechanically and in line with other 3rd level spells. However thematically a stinky cloud is more a Druid kind of thing. I think its probably better to merge these into one spell, like Glitter Cloud and replace the level 4 spell with something more interesting. I picked up Modify Memory from the SRD which is actually a really nice fit. I liked the idea of a druid having a stink effect like a skunk so I made a new stinky spell cantrip for them. There's a lot more tweaks and pokes I've been making as I have been looking through the spell list correcting some of these issues.
I really wish I could get rid of the level 0/cantrip label and just re-number the spell levels 1-7. That would be a lot more streamlined, but I don't want to do it because I think it would really break a lot of comparability for new Beacon DMs using d20 source material. So I am leaving it as is for now.
One of the larger changes is I'm considering is to remove Read Magic as a spell. This spell is so essential to a arcane caster that it should be a class ability. Who's not going to take Read Magic? They take it or they won't be able to learn any new spells or use scrolls? So its a wasted slot in the list. One benefit to making it a class ability is that you can let other classes do it too, I was thinking of having rogues be able to read magic scrolls at some point or maybe making it something anyone could do with sufficient communication skill or something. To be clear, not thinking of extending magic use to other classes, just thinking it might be fun letting a non magic character try casting a hella dangerous-scroll.
Spellbooks and Learning Spells
Spell books are needed to keep track of what spells arcane casters have learned. When casters find new spells they can write them into their books and then those new spells are available to be cast. So spell books are a way to turn magic into treasure that can be discovered, but also a way to give magic users things to spend treasure on, since they don't buy expensive armour or weapons generally. It costs magic users time and money to write the spells into their books so this is additional cost to level up vs what a fighter or rogue would need to spend but that's an not necessarily a bad thing. How else can magic users gain spells? Presumably by training with a teacher or studying. Both those options line up with other class training costs and downtime so I don't see a problem there.
Just from a physical perspective, spell books are hard to manage - how big are they? Can they get wet? Can they be lost or destroyed? Can they be stashed someplace? I thought about removing spell books and just abstracting this mechanic, but I think that these are interesting questions that can be handled in game so I'm inclined to keep spell books as they are.
Making potions and scrolls (and magic items):
The other thing I've been pulling my hair out over is players making magical things like potions and scrolls. I really wanted to have this working since players generally like the idea, hell I like the idea, but part of me just wants to remove this from the game entirely. The v6 rules have some simple ideas for creating potions and scrolls but its not well balanced and I'm concerned that it puts a huge cost burden on magic users since they are going to be torn between spending cash making potions and scrolls vs. leveling up. I guess the party could all chip in to make potions or scrolls but that makes it now like buying magic items from a shop with extra steps.
I'm leaning towards dropping this entirely. There are strange forces out there who can make magic stuff but its not the PCs and that's quite OK by me. Not having to deal with PCs making these items makes treasure easier, it takes away the problem of balancing magic item creation system against other class spending or trying to figure out why the PCs don't just make dozens of scrolls to get past their HP based spell limits. PCs are there to have adventures, if they wanted to make scrolls or potions they could sit in a tower all day and do that instead, that's a different game. If you want to run an adventure where players make a magic item you can do it as a one off adventure with all sorts of crazy items to collect and strange challenges to overcome. Its magic, the rituals might not even work a second time. I think its all around much better for magic in general to be mysterious and part of the world/campaign and not something codified in the rules. NPC magic users just don't follow the same rules as PCs and that's OK, in fact its better than OK since it makes them interesting opponents instead of half-assed PCs. Let those NPCs craft all the goodies and the PCs can find them in dusty old libraries and forgotten tombs.
The only reason I am still considering keeping these things in the game would be to have an excuse for the Crafting skill, and that's kind of a crappy design. If the Crafting skill needs entirely new mechanics to justify it then its not essential or it isn't balanced with the other skills enough.