I'm not sure if this belongs in Suggestion/Homebrew or here, but since I haven't thought of a solution yet and I'm asking for input, I think it fits better here.
Shadow barbs, flame blade, icicle dagger, and the like. The flavor is great, but they tend to be, well, crappy. Almost always cleric/oracle and sorc/wiz, almost never for the magus, and usually too high a spell level to come in handy at low levels.
The characters that get access to them have almost no use for them. The characters that could use them can't get access to them. They might see use if a melee cleric or oracle needs a backup weapon, but that requires sacrificing a spell known and memorized or a spell slot.
You could make a magic weapon based on them, but since all they do is make a temporary magic weapon permanent versions of them tend to be somewhat boring.
How would you make these spells viable without making them must-have? I've considered making them options for certain races' SLAs or feats, but they seem too good to be SLAs or prerequisite-less feats, but not good enough to warrant level prerequisites, especially since they'd have to be 1/day with a duration of only 1 minute a level.
It's entirely possible to make a cleric, oracle, sorcerer or wizard who doesn't fear melee. Your assumptions are wrong here.
Also, why assume that your homebrew has to be 1/day for 1 min/level? I don't understand why you're making this assumption for your own work. If you'd rather have it be something else - maybe 1 min/day in 1 minute increments, maybe 10/min/level, maybe 3/day for 1 round/level - do that.
Alternately add some spells to the magus list in your campaign. If you want the magus to be able to cast flame blade it's some of the easiest homebrew that there can be.
Samsarans get them.
Samsarans get all the nice toys.
Is there any other race to make a magus with?