Oh, that's not even a question. Won't touch anything with DRM (or requiring a client even to download, for those who see that as in any way different) even if free.
Losing characters really sucks... Having some party members drop out / die in scripted sequences, as part of the story, in a way that makes sense and has an impact, ok, story over gameplay considerations, definitely for that, assuming the story's good enough. But if they can simply get killed permanently whenever (combat, trap, random event, ...), or the whole mechanic is built on replacing them like that, or if the main character can be lost with the game continuing, as you say, no thank you. Unless we're talking of hired mercenaries or something of the sort, they're characters, or should be, not just a sum of skills.

Back on topic, about available spells and what I was saying about maximum total complexity, there's something in a MUD (though I'd really call it a text MMORPG) that I played, Materia Magica. Using present tense because game still exists, with a handful of players from what I heard, but describing what I remember from back when I played it, mid-'00s mainly. All skills have a certain complexity, classes gain complexity proficiencies at different rates each level, skills (including spells, all seen the same) become available as you reach the required complexity, but to cast a spell you need it either memorized or in a spellbook you hold, and there's a maximum complexity you can memorize. So you have the required proficiency to cast the spell, but that's worthless unless you find a scroll with it and scribe it in a spellbook (spellbooks have max complexity they can hold too), and then you may have loads of spells in various spellbooks but have to decide which ones to memorize at any time to be able to cast right away, if you don't care to hold something else in the off hand you need to decide what other spells to put in a spellbook you hold in the off hand (also keeping in mind that if you're blinded or it's too dark and you can't see in the dark you can't read from it, memorized spells are all you have then), while to access any others you'd need to swap spellbooks (minor nuisance for non-combat stuff, but quite a problem in combat, missing rounds, and needing prepared aliases for it because if you'd be to type the commands you'd miss a whole lot more). Struck me as a WAY better way to do it than the D&D way. (Note: Mastered (100%) spells are always memorized and can be cast while webbed too. And yep, everything is trained through use and also by trainers. Trainers use practice points (for both skills and attributes), a few gained while leveling, most from quests and such, use is just... use, just that it's darn hard to train through use without getting some passable proficiency first, since you keep failing. However, trainers can only go to 75% for the vast majority of skills, past that you can only train through use.)

I believe that's only true in 4th and 5th edition.

In 3.x, cantrips exist but must be prepared or memorized like other spells, and you have only finitely many slots for them; furthermore, 1d3 damage to a single target isn't going to cut (well, freeze, since it's a cold spell) it.

In 2e and earlier, there is no formal spell level; rather there's a first level Cantrip spell, which is like Wish in that it is flexible and its behavior isn't completely specified; the difference, of course, is that it's much weaker. I think it may be specified to not be capable of dealing damage, so it wouldn't work for this purpose, not to mention that 1st level spells are still limited use. (2e Wild Mages get a 1st level spell that is capable of emulating any other known spell, but which has the drawback of being highly unpredictable.)

I wanted to add something else here: Fell Seal (current game I'm in love with, I can't help it.)

When battles start, characters start at ZERO mana [yes, there's an upgrade one job gets to start at a number higher than zero]. They regenerate a little every turn (every turn). A lot of spells cost a lot, so you have to wait out a few turns of doing no-mana-cost actions (or even more if you continue to cast low-mana-cost spells) before you can cast your big spells. I like it, how it affects momentum in battles likes that. It does kind of make the "max MP" stat all-but-useless after a few levels, though.

(Related: 13th Age tabletop RPG has its "escalation die" that also is a great way of showing battle momentum: every turn, it increases by 1, and all players [and a few rare, scary-strong monsters like dragons] add it to their rolls. And, of course, there are some skills that manipulate it, like the commander "everyone take a breather" skill that has all allies heal, but drops the escalation die.)

Other cases of this sort of thing:
Tactics Ogre: The Knight of Lodis (GBA) has a similar mechanic. There's no way to *start* with MP, but there's a 0MP spell that damages the user to restore an ally's MP, and another that reansfers MP with the ability to transfer more MP than the character has.
Romancing SaGa: Minstrel Song (PS@), as I mentioned, does something along these lines with its BP stat, but it starts at a percentage of its maximum determined by the character (note that characters with more starting BP typically have lower BP regeneration, but that's not a strict rule; Claudia starts with only 20% but can (eventually) gain up to 7 per round, while there's one temporary character who starts with 60% but can't possibly regenerate more than 3/round (and is unlikely to reach that 3/round figure because he's only in your party temporarily, unless you make use of a glitch that was patched out of the English version. Note that having starting BP and (to an extent) BP regen be affected by the maximum keeps the maximum value meaningful, as does the existance of rare consumables that restore BP fully.