Creating non-standard spell slots

[wdmartin]

I'm working on creating a homebrewed 3.5 port of the 3.0 class "Runescarred Berserker", originally from the sourcebook "Unapproachable East."

I think I've got the class mostly working; the one glaring exception is spell slots. The class gets seven spell slots, total. The number of spell slots never changes, but any one of those slots can be used to prepare any spell level the character is capable of casting.

I've treated the class like a wizard for purposes of learning spells -- that part was pretty straightforward. But currently I've got no UI for prepping spells, because the built-in spell slot system assumes any given slot is only valid for a specific spell level.

Any suggestions on how to approach this?

Here's the class description I'm working from:

Runescarred Berserker

Requirements

Base Attack Bonus: +7
Skills: Intimidate 5 ranks, Sense Motive 2 ranks
Feats: Iron Will

Hit Die: d10
Skill Points: 4 + Int
Class Skills: Climb, Craft, Handle Animal, Intimidate, Jump, Knowledge (Arcana), Listen, Ride, Sense Motive, Spellcraft, Survival, Swim.
Weapon and Armor Proficiency: None

Features

Scribe Runescar (Sp): At 1st level, a runescarred berserker learns how to carve a runescar into her own skin. A runescar is a means of storing a spell, much like a scroll. A runescar berserker can only cast spells by crafting them as runescars; she has no other spellcasting capability and cannot use spell completion or spell trigger magic items based on spells from this list.

The berserker can scribe first level spells at level 1, second level spells at 3rd level, third level spells at 5th level, fourth level spells at 7th level, and 5th level spells at 9th level. She must have a runestone for the spell she wishes to scribe (see Runestones below). Scribing a runescar takes 1 hour. A berserker can only inscribe runescars on her own body. If the spell requires material components, the berserker must supply these at the time the runescar is crafted. The act of scribing a runescar is painful and deals 1d6 points of damage per spell level at the end of the scribing time. The berserker is free to heal this damage by any normal means afterward—the runescar remains until activated.

Runescars are considered arcane spells. The caster level for a runescar is equal to one-half the berserker's base attack bonus (rounded down), but may be set lower if desired (minimum 1). If necessary, the saving throw for a runescar spell is equal to 10 + the bersker's Constitution modifier + the spell level.

A runescarred berserker can bear no more than seven runescars at any one time: two on the chest, two on the upper arms, two on the backs of the hands, and one on the face. Runescars are dormant until activated and cannot be dispelled (although they can be suppressed).

To activate a runescar, the character must take a standard action and touch the rune. Runescars do not require somatic, verbal, or material components when activated, and do not suffer from arcane spell failure due to armor. All runescar spells target only the runescarred berserker or an item in her possession, even if the spell scribed could normally be bestowed on another subject.

After activation, the runescar's magic is discharged, and the rune fades to nothing but a faint outline. Typically, a berserker's skin is crisscrossed with dozens of old, discharged runescars.

Runestones: In order to inscribe a runescar, a runescarred berserker must have a runestone as a reference. Each runestone contains a single spell. She cannot prepare a spell for which she lacks a runestone. Upon becoming a runescarred berserker, the character gains 2 runestones containing spells of her choice from the runescarred berserker spell list.

Runestones Gained at a New Level: Runescarred berserkers perform a certain amount of experimentation with runes during downtime. Each time a character attains a new runescarred berserker level, she gains one runestone of her choice. The free runestone must be of a spell level she can cast.

Creating Runestones: A runescarred berserker may copy an existing runestone. Doing so requires a full day of work and a successful Spellcraft check, DC 15+the spell level. A suitable stone may be purchased for 5 gp, or located for free with a DC 20 Survival check. This allows her to learn new spells from another runescarred berserker, or from runes discovered in the course of adventure. She may also use this ability to create backup copies of her runestones. She cannot create runestones from scrolls or spellbooks.

Extra Rage (Ex): A runescarred berserker gains additional daily uses of the barbarian rage ability. At 2nd level, she gains one additional rage per day; at 5th level, she gains a second additional rage; and at 9th level, she gains a third additional rage. For example, a barbarian 8/runescarred berserker 5 can rage three times per day from her barbarian levels, plus two more times from her runescarred berserker levels, for a total of five rages per day.

Ritual Scarring (Ex): Through frequent disfiguration of her own skin, a runescarred berserker gains a +1 natural armor bonus to AC at 3rd level. This increases to +2 at 6th level, and +3 at 9th level.

Runic Rage (Ex): At 4th level, when a runescarred barbarian enters a rage, she may choose to activate one of her runes as a swift action.

Damage Reduction (Ex): Starting at 4th level, a runescarred berserker gains the ability to shrug off some amount of injury from each blow or attack. Subtract 1 from the damage the berserker takes each time she is dealt damage from a weapon or natural attack. At 7th level and 10th level, this damage reduction increases to 2 and then 3 points. This overlaps (does not stack with) damage reduction from any other class feature.

Greater Rage (Ex): Starting at 8th level, a runescarred berserker's rage bonuses become +6 to Strength, +6 to Constitution, and a +3 morale bonus on Will saves. Her AC penalty remains —2.

Level 1
Cure Light Wounds
Endure Elements
Enlarge Person
Feather Fall
Jump
Magic Weapon
Protection from Chaos/Evil/Good/Law
Returning Weapon
Shield
Stone Shield (Pathfinder spell)

Level 2
Cure Moderate Wounds
Bear's Endurance
Blur
Cat's Grace
False Life
Fireburst
Force Sword (Pathfinder spell)
Resist Energy
See Invisibility
Spider Climb

Level 3
Blood Biography (Pathfinder spell)
Cure Serious Wounds
Displacement
Fly
Force Hook Charge (Pathfinder spell)
Haste
Magic Weapon, Greater
Magic Circle against Chaos/Evil/Good/Law
Protection from Energy
Versatile Weapon (Pathfinder spell)

Level 4
Cure Critical Wounds
Dimension Door
Fire Shield
Ghost Wolf (Pathfinder spell)
Stoneskin

Level 5
Contingent Energy Resistance
Fire Burst, Greater
Indomitability
Interposing Hand

[Sendric]

I think how I would do this is to make the spells into Custom Abilities, then make them Spell-Like so that they appear in the spells tab.