Something along those lines, yes.
Not being a manufacturer or LFS, I don't care if it is something that is sold, or something that people make themselves with a detailed recipe. Something like, take 1 box baking soda, mix together with 1 box of (whatever turns out to be a good, cheap CaCl2 source), and then add as much as necessary each day to your tank to maintain alkalinity (you'd only need to ocassionally measure calcium, or vice versa).
The main point is to make a single additive that was equal in cost to CaCl2 and baking soda supplements, but that would eliminate the calcium/alkalinity roller coaster. In others words, an idiot proof single solid supplement that can be added directly to the tank.
In reading chemistry problem posts, it appears that people frequently have a substantial problem with that issue.
Since it would largely be a mixture of CaCl2 and NaHCO3, it would still suffer from the slow climb in sodium and chloride that these additives suffer. In part, that's why the MgSO4 is there: to at least keep Mg++ and sulfate from declining. Whether most people also have a sodium or chloride issue is less clear. Many of the people that would use such a supplement have relatively low calcification tanks, or else they would have already typically switched to a two-part additive, limewater, or a CaCO3/CO2 reactor.
In such low calcification situations, the trend toward raised Na+ and Cl- is very slow. Add back magneisum and sulfate, and I'm not sure that you're missing much (maybe nothing, depending on the impurity profile, there might already be too much of most everything else).
