Make it end to end D-loco because what I feel is, it would be difficult to arrange a loco change at Bareilly Cantt. Also, if you do it at LKO, then also no use. TIP: Extend upto Ghazipur City.
EDIT*: Do like this -- Aligarh Lucknow : D-loco. Lucknow - Sultanpur - Varanasi - Ghazipur City : E-loco.