If you don't want to limit yourself to channeling, but don't want to go full evocation either, you could adopt "flavored evocation". Basically, you take evocation, but you flavor your 5 elements by your original element, splitting the applications into subsections.
Sponsored magic can already be cranked up as high as you want by tapping into your sponsors power. If you don't like the debt mechanic, you should think about taking channeling/ritual instead, I think.
If you remove the column from the equation, specializations will get absurdly powerful, which you were worried about in the first place, that's why I mentioned it. 3 refresh will grant you a maximum of +3 on one application in the column system, but a +6 at best without them. That's the big difference between focus items and specializations. Specializations have to stack up in the column, but they can grow as high as you like. Focus items don't have to stack, but they are limited in their number, and you have to divide your points into offensive/defensive. If you take away the column limitation of specializations, they will pretty much always outweigh focus items in terms of bang for your buck. You can, of course, still do that, just keep in mind, that this is what you are dealing with, then.