I had to read this a couple of times to get your meaning. I think it's a nice idea in theory that has already been effected by the Dev's introduction of Aurora, Protective, and (to a lesser degree) Denouncement and Valiant spell lines. The caveats are: Light shares a timer with Protective and so is obsolete. Burst has recast and spell gem lockout issues. Touch has a long casting time. Of these 3, only Burst earns a spell gem regularly. So there really isn't much improvement to be had there (barring entirely new spells) that would be easily gained by upgrading the ToT lines (especially leveraging the Protective line's beneficial spell mechanics).