While not being a mania-player I'd like to casually throw in that a high combo will naturally assure the play a minimum degree of accuracy until the combo is broken. As such it will be rewarded in both components of scoring and not only the combo-component. This takes away the biggest part of a potential advantage another player could get from having a better accuracy while having less combo. This results in combo (while "only" holding 20% weightage) getting a scoreimpact that will be experienced as stronger than that in a practical environment.
Same thing from a different perspective:
When you miss a note you will lose your combo and therefore lose combopoints but you will also lose accuracypoints. It's always punishing you in both areas. If combo is supposed to be the thing that awards points on consistency in not missing then a miss should not reduce the accuracy. From a practical standpoint it doesn't make any sense to say that a combobreak should not reduce your accuracy but it would be the only meaningful solution if you want to have the combo- and the accuracy-component contribute score separate from each other without automatically favoring combo.
tl;dr
Any scoringsystem that gives combo an own value will automatically favor combo over accuracy as a lack of combo always includes a loss in accuracy. The higher the advantage of a fullcombo vs halfcombo is, the less impact accuracy can have.
Same thing from a different perspective:
When you miss a note you will lose your combo and therefore lose combopoints but you will also lose accuracypoints. It's always punishing you in both areas. If combo is supposed to be the thing that awards points on consistency in not missing then a miss should not reduce the accuracy. From a practical standpoint it doesn't make any sense to say that a combobreak should not reduce your accuracy but it would be the only meaningful solution if you want to have the combo- and the accuracy-component contribute score separate from each other without automatically favoring combo.
tl;dr
Any scoringsystem that gives combo an own value will automatically favor combo over accuracy as a lack of combo always includes a loss in accuracy. The higher the advantage of a fullcombo vs halfcombo is, the less impact accuracy can have.