Multiple ballasts such as you describe will not be a workable or safe solution. There are ballasts that are mode-switchable (35/55) but as far as I know none of them are automotive-certified. More than that, though, all of this "55w ballast" stuff is illegal and unsafe.
Rule 11 of this board prohibits advocating illegal or dangerous activity.
That's actually why, when I ordered the new stuff, I went with all 35W hardware. This was more of a curiosity than anything. Putting aside legality and safety concerns, I wouldn't bother if only for the number of added failure points involved. It's an interesting idea to have the high beam switch also crank up the low-beam output, but it's just not worth the nonsense entailed (let alone the risk.)
Interesting note: at the moment, I have new ballasts and bulbs on one side and old stuff on the other, because my car is a pain to work on. My new HYLUX 35W ballasts significantly outperform the super-generic ballasts a local shop had installed, at least in the barely-used high beams. The alleged 55W ballast on the low beam is still putting out more (and warmer) light than the 35W ballast I just installed, but the gap is not *that* large. It's noticeable and I'm a spoiled and picky MFer, but still a far cry from the incans my wife's car is running. All that said, if I had been a little less lazy and did it myself the first time around with quality hardware, I wouldn't have bothered with the 55W "upgrade" in the first place.