Flame Arrow Strikes Back

Everyone who's ever read a spell list has been puzzled by the presence of Flame Arrow on the 3rd level Magic User spells list.  How could a spell that ignites (1/level) arrows, when touched by the MU, thus allowing them, should they hit their target, to inflict one (1) extra point of damage--be allowed to occupy the same stage as Fireball, Lightning Bolt, Fly, Haste, etc.?  Any party with a torch can do the same thing without an MU, so why would any self-respecting Thaumaturge forgo one of the numerous useful 3rd level spells for this turkey?  The answer is simple: no one would and and no one ever has, ever.  So either Flame Arrow needs to be demoted to the zero-level spell list where it belongs or it needs a serious upgrade.

Hackmaster of course does it better, allowing an option that essentially lets the MU cast a firebolt that causes 4 or 5d6 damage; it's sort of a mini-fireball without all the risk to your dungeoneering cronies. But I'd like to take the idea behind the AD&D version of the spell and maybe make it worthy of being a spell that a 5th level MU would opt to have in his pocket.

Proposed upgrades:

• Not just arrows and crossbow bolts, Flame Arrow will also cause sling bullets, spears, thrown daggers and heaved rocks to turn into incendiary grenades.  Heck, even a snowball will do the trick.
• No touch necessary, rather all missiles launched from within, say, 1"/level of the MU will burst into flames en route to the target.
• Enflamed missiles continue to burn for the duration of the spell (1 round/level) after striking their target, causing additional damage or at the least leaving small fires scattered throughout the combat zone, igniting wood floors, wallpaper, fields of dry grass, leaf piles, etc.
• Piercing missiles--arrows, daggers and the like--will inflict 1d6 additional dmg immediately and will continue to do so until removed or the duration of the spell ends.  Removing a blazing arrow or quarrel in such conditions inflicts and additional 1-4 pts of dmg.
• Non-piercing missiles such as stones, hammers, rotten tomatoes, would inflict 1 additional point of damage on contact but would not inflict additional damage through the duration of spell unless the target or it's clothing were ignited by the impact.
• The fire is magical. it does not burn up the missile, nor does it need oxygen to burn, thus it can be used underwater, though it will not be able to ignite other objects in such conditions.