One of the complaints occasionally leveled against the default GURPS magic system is that the Enchantment system appears to have been designed to convince the players not to use it (that may not have been the actual intentions of the designers, but that's how it looks to some of us), without considering that this means the in-setting NPCs would likewise be very unlikely to use it (for reasons discussed in
this thread, among other places). This is fine for some settings (e.g. those where logic need not apply to worldbuilding, or where about 90% of the enchanted objects should be staffs, powerstones, and single-use items, and most of the rest are weird artifacts created by long-lived races for whom taking a decade or two off for an art project is a minor issue at worst), but it's not exactly generic.
There are a number of ways to fudge this, of course. Probably the easiest is to just make Slow and Sure Enchantment faster, e.g. eight points per day instead of one per day. It occurred to me a few hours ago that there was an option that I don't think I've seen explored: The spell system is already tied to the Alchemy/Herb Lore system in one place, that being the Lich spell and potion (
GURPS Magic pp159-160). So, the basic concept in my mind is that enchantment could instead be done by creating an alchemic charm (or treating an existing object with Alchemy or Herb Lore) that can have a spell permanently impressed on it by casting it ceremonially during preparation. The charm, once completed, can then be used to cast that spell or those spells (depending on style of play, you may be able to load only one spell per charm, but attach multiple charms to a single item, or you may be able to load all the spells into one charm). The rest of the Enchantment college might remain as it's own thing, or be added to Meta-Spells or split up into several colleges.
The specific criteria of the Enchant elixir most likely depends on the setting. My current thinking is that the brewing time is one week per one hundred points, with the spells being loaded into the charm at specific stages in the brewing, but there are certainly other options. A large part of this is a desire for something close to plausible economics: Given the level of skill and number of workers that you would expect this to involve, could the costs of the resulting items be low enough that people would buy them (and thus low enough to be worth making)?
Also, an answer that can vary
a lot from game to game: Would these magic items plausibly be as common as you need them to be for your setting to make sense?