Regarding distance - Etah-Tundla existing distance is 74Km. Add 33Km of KSJ to Etah and 29 Km from Tundla to Agra Cant. Thus Kasganj via Etah to Agra Cantt is 136 Km.
Whereas Existing route via ACH is having 163 Km. So just 27 Km rout Km saving but problem of line crossing at Tundla. You decide.