Semi-side comment.
I don't think the major issue with caster vs non-caster balance is mainly how often they can cast, although it is obviously a factor to some degree.
The major issue, imo, is that casters have a much more versatile primary ability. Caster and non-casters both get all the various random skills with their various leanings, however their primary ability is Spells (for the casters) and Weapons (for the non-casters).
The non-caster has, as their primary ability, a far superior weapon ability. The benefit is they can do damage, with a weapon, either in melee or with a ranged weapon.
The caster has, as their primary ability, far superior access to a large variety of spells that encompasses much more than just "cause physical damage to your target".
Add to this that casters, surely at least by higher levels, will start developing at least one weapon skill. The caster needs to spend (in RMSS) 9dp on a weapon and, aside from profession bonuses, will eventually get halfway decent at that weapon skill. Yes, it will take some time only being allowed to develop one rank at a time, but I think it's not too unrealistic to say that a non-caster would be doing this each level. By 10th level they'd be ok at it and by 20th they might be pretty decent. So, eventually the caster becomes mildly effective with a weapon.
Now take the non-caster. In order to develop skills they, at best (if I remember correctly) must pay 12-25 points on a single rank in a single open spell list. Developing 10 ranks in a single weapon skill is cheaper for the caster than developing 10 ranks in a single spell list for the non-caster. The non-caster also has to pay a lot for Power Point Development. Also, having a low casting ability is more dangerous that having a low weapon ability when trying to use those respective skills. Also take into consideration that a caster developing a single weapon skill bring them closer to be able to perform a non-casters function than developing one spell list brings to non-caster to performing a casters function.
Yes, the non-caster can develop lots of weapons, but all they do is cause physical injury to the target. The caster has a vastly larger array of abilities as a result of the variety of spell lists they can develop.
The result is that the non-caster outperforms the caster at low level because their function is more specialized while, in the long run, the caster ends up much more diversified. This is one of the ways in which I often end up with slightly more 'powerful' characters in our gaming group. I rarely buy up skills multiple ranks at a time, I buy a lot of single ranks in all the skills I'm interested in and, as a result, end up with superior skills over the long haul. This happens pretty much unintentionally with casters vs non-casters due to the nature of their primary ability.