Actually it would be the best to include 'salt' type addition, where user would specify by himself how many ions of which kind that salt brings in. CaCl2 for instance is available as anhydrous or hydrated with different amount of water (2- and 6-hydrate being most common) - 1g of CaCl2(H2O)x brings different amounts of Ca and Cl into wort. Same for CaSO4. BS for now (I didn't check thoroughly though) calcuates as if all salts were anhydrous.
Other improvement would be a checkbox for adding salts to mash only, ie. overal water profile is calculated against total volume, but mash pH against mash volume only. Or to differentiate when salts are added (mashing, sparge water, kettle). Adding all salts into mash is quite a common technique for brewers using with RO water that contains close to none ions, allowing 'oversparging' with runoffs never reaching ph of 6.