Sure what ever works, just remember that as a solution it is unstable, as you said make it, use what you need, and toss the rest.
Half a Campden tablet is like 5 cents, takes a lot of 5c to pay for a scale that you would trust. Absolutely not a problem either way and doing what works best for you is the obvious call.
Personally I would be hard pressed to justify making the decision either way based on dollar$, whether it costs 5 cents, or I saved 3cents by mucking around weighing our stinky powder that makes my eyes water and nose run, isn't something that's going to get me too excited.
I have a carbon filter so its moot, 50% for brewing and 50% because I like the taste of filtered water in the fridge and the coffee maker, so I haven't got to muck around with it any more. I think over a couple of decades I have picked up a bit of a chemical sensitivity to SO2 and these days avoid it where I can.
Seriously unimportant how you choose to get rid of Cl, getting rid of it will help you make better beer.
For all those brewers who have a pleated filter you can get a Duel Cartridge, Particulate and Carbon in the one filter, last one I got was less than $20 at the big green shed, bit of creative plumbing and you would have a water filter that should last a year or more for brewing, you still have your pleated filter for beer if you are so inclined.
Mark