Vortex Campaign

An idea for a d20 campaign where the group consists largely of pickup players or those with unreliable schedules, where the players (or even DMs) may not be constant between sessions.

The campaign takes place in a universe where periodic vortices appear and disappear, grabbing people and sometimes moving them around, exchanging them with other people, etc. At the end of each session, the whole party is grabbed by a vortex. At the start of the next, the players that are toss out of a vortex. Sometimes the group is the same, sometimes not. Often the location is the same, but sometimes it is yards, miles, continents or even universes away. In this way, guest DMs can run whole adventures without real constraint, without interrupting a mainline story. Sometimes, a vortex will occur mid-session.

Benefits

To player perception, when sucked into a vortex, they are pushed out instantly. In reality, some time passes within the vortex that the player's do not remember. In this nether realm, they exert some subconscious control over the primal forces at work within the vortex, and can use it to improve themselves.

On each trip through a vortex, a player may choose to do one of the following:

Heal 50% of their total hit point total
Reset their odd level spells to how they were at the start of the day. For casters that don't need preparation, this refreshes their compliment of spells cast per day. For those that need preparation, memory of those prepared at the start of the day returns.
Reset their even level spells to how they were ate the start of the day.
Replace one known spell for another of equal level. For non-preparation casters, this looses one known spell and gains another of the same level. For those that use spell books, one spell disappears from the book, replaced by another of the same level.
Replace one bonus feat for another. Fighters can forget one bonus feat and learn another in its place. Other classes that get a choice of feats at certain levels (e.g. monks at second level) can change the choice they made. This cannot be used to eliminate feats acting as prerequisites for others, and the character must meet the requirements for the new feat learned.
Move a point from one ability score to another.
Move four skill points from one class ability to another class ability or abilities. You still cannot exceed maximum levels.
Move two skill points from one cross-class ability to another cross-class ability or abilities.
Training needed for a new feat is magically learned. This doesn't provide the feat itself, merely the training needed to learn one when it is available. If the campaign doesn't require training for feats, this is a moot choice, but in training-based campaigns, this allows players to get the training they need easily.
Training needed for two cross-class skill points.
Training needed for four class skill points.

The Cost

These transmutations do not come for free. If a player chooses to use one, there is a random cost applied. The cost is always applied after the benefit. Costs include:

The benefit is undone.
Another benefit is applied at random
Character loses 1d20 x 10 xp
Character loses 1d20 x 50 gp
Character permanently loses 1 hp.
Character takes a point of random ability damage