Just to continue contributing, these are the major changes I would make to the problematic spells from the RQ Companion. Again the idea is to minimise changes wherever possible and to work within the existing MRQ framerok. I've only flagged the key elements here - the rest are on the wiki.
Dominate (Species
In addition to the normal cost of the spell, the sorcerer must charge the spell with an additional number of Magic Points that are least equal to the target’s Magic Points or else the spell is automatically resisted.
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Any time a dominated creature is ordered to perform an activity which would cause it severe harm or expose it to severe danger it may make an opposed roll of its Persistence versus the Spell’s Magnitude*10. If the attempt succeeds the spell is broken. If the dominated creature fumbles the attempt, the stress kills it instantly.
Fly
Each point of Magnitude can levitate up to 15 ENC of a single object, 3 SIZ of a single living being or can increase the movement speed of the target by 1m. For the purposes of the spell, treat 5 ENC as equivalent to 1 SIZ. As a guideline assume that 1 SIZ equals roughly 5kg. Example: to fly someone with a SIZ of 13 who is carrying 12 ENC would require enough magnitude to fly the equivalent of 16 SIZ, which is to say 6 Magnitude.
Shapechange
(Not a lot of people realise just how impossible this spell is..)
The spell needs 1 Magnitude for each 3 points of SIZ (or portion thereof) of the target. At the time of casting the caster may charge the spell with any number of Magic Points. Each MP charged this way allows the caster to add or subtract one point from the target’s STR and SIZ in its new form (to a minimum of 1). I The target’s other Characteristics cannot be changed in this way...
Example: to change a SIZ 13 man (STR 11, CON 12, DEX 15, INT 13, POW 10, CHA 9) into a SIZ 1 mouse the spell needs to be cast at magnitude 5 and the caster would need to spend an additional 12 Magic Points which would leave the target as a STR 1, CON 12, DEX 15, SIZ 1, INT 13, POW 10, CHA 9 mouse. If on the other hand, the sorcerer wished to change the target to a SIZ 22 bear, then it would cost an additional 9 Magic Points and the target would end up as STR 20, SIZ 22 bear.
Smother
Each point of Magnitude will cover three points of SIZ – thus a Magnitude 4 Smother would be enough to cover a SIZ 12 target. When the spell begins, if the target fails to resist but scores a Partial Success (i.e. they made their Persistence test but lost the opposed roll) then it is able to gasp in one last breath before Smother cuts off the ambient oxygen supply otherwise it will start drowning in the next Combat Round.
Tap (Characteristic)
Instant
Tap will only work if its Magnitude is greater than the target’s specified Characteristic. For each point of Magnitude in excess of the Characteristic, the target loses 1 point of the Characteristic permanently. Thus a Magnitude 6 Tap Strength spell cast against a target with a STR of 4 would tap 2 points of STR from the target. Tap spells have no effect when used against Fixed characteristics such as INT and CHA for animals. ...
If the sorcerer gains more Magic Points through Tap than his normal maximum, they will disappear at a rate of 1 per minute after the spell is cast.