Maybe I misstated my first post. I totally get that many reserve feats, including those that do direct damage (unless the damage is further scaled back) don't make sense to grant to first level characters because they would do more damage or whatever effect than the spell held in reserve. I'm just wondering if there are some other reserve feats that could (in your opinion) be granted to first level characters.
For example, as a dm, would you have a problem with Aquatic Breath being used by a 1st level character? If you did have an issue with it, could it be scaled back based on the spell level held in reserve that you would allow it?
... Aquatic Breath doesn't scale. You pretty much can either breath water, or you can't. Water Breathing is also a 3rd level spell, so picking up the ability to do the same thing indefinitely before you get to the point where you can cast it yourself? Probably not particularly balanced.
But let's go through all the ones in Complete Mage, just for grins.
Acidic Splatter? At 1st level, even with a 1st level spell, it'd be doing 1d6 - which is the same as Magic Missile or Shocking Grasp at that point - all day long. It's not exactly weaker than available spells.
Blade of Force: Eh, this one isn't particularly grand - it's really designed for gishes - but you've got what amounts to half of an at-will Magic Weapon spell (you're only getting one attack per round at that level, and you get +1 damage on it, and there's not much else to use swift actions on at that point), except that it also negates incorporeality (which Magic Weapon doesn't). You've got something as strong as Magic Weapon, except you can use it constantly - again, the effect is better than a 1st level spell.
Born Aloft: While not very grand, it makes very light of most obstacles - and the feat doesn't scale. Castle walls? Not an issue. Bridge out? Who cares? And so on. At a point where you've got Overland Flight available, this isn't an issue... but, oh, wait - you can't get it until you've got fifth level spells....
Clap of Thunder:
If you let a 1st level spell power it, this is Shocking Grasp, plus a status effect, at 1st. No.
Clutch of Earth:
Eh, it doesn't do much useful. This I might let slide... but who cares?
Dimensional Jaunt: No - grappling is about the only method of shutting down low-level casters (without killing them, that is). This is a get-out-of-grapple free feat. No.
Dimensional Reach:
This is very highly situational. At 1st, it doesn't matter - you could just pick the item up anyway 90+% of the time.
Drowning Glance: Doesn't scale, and Exhaustion is a pretty nasty status effect, when it comes down to it.
Face Changer: Does everything Disguise Self does, but with no real duration limit (other than stopping once per minute to renew it - but no visible effects when you're doing so, so....). Again, no.
Fiery Burst: Already went over this one.
Hurricane Breath: If anything, it's stronger if you can have it at 1st level than it is if you can have it at 20th. I might let it work... but who's going to really want to?
Invisible Needle: Okay, this one would be balanced enough - you'll have better luck with a light crossbow, though.
Magic Disruption: ... doesn't really do much with a 1st level spell, although the Concentration check is decidedly annoying at that level, what amounts to a +2 to the save of nearly everyone in the party? That's fairly strong for 1st.
Magic Sensitive: Just cast detect Magic. Really, it's a cantrip. Still, this one isn't exactly game-breaking to use 24-7 at a range of 5 feet....
Minor Shapeshift: One of the few highly useful reserve feats to being with. No, you can't take it at first. There's too many useful things on its list.
Mystic Backlash: One point of damage? Eh, waste of an action, especially if you can touch the target anyway. You're generally better off readying a Magic Missle or something (by a lot). Might let it if someone was insistant.
Shadow Veil:
20% miss chance is just mean. No, you can't have this at 1st.
Sickening Grasp:
-2 to basically all rolls, no save? Umm... no. Not at 1st.
Storm Bolt:
At 1st level, is superior in basically all ways to Shocking Grasp. No.
Summon Elemental: For one, what would you have it summon? For two, regardless of what you brought in, you'd suddenly have no need for a trapfinding rogue. It's one thing to get rid of the trapfinding when the Rogue's reached a point where they're all gone anyway - it's quite another when traps are still significant.
Sunlight Eyes:
Darkvision's a 2nd level spell, and this is superior in a lot of ways (it lets you see through even magical darkness). So no.
Touch of Distraction:
This one I might let fly with lower requirements - it doesn't do much of use, after all. Sickening Grasp is stronger.
Wind Guided Arrows:
Eh, maybe. +2/-2 to an arrow that's shot at a target within ten feet? Not doing much.
Winter's Blast:
Using a 1st level spell to power it, at caster level 1, it's the cold-version of Burning Hands - exactly.