In the Greek there is no purpose clause for "for the remission of sins," just a prepositional phrase with eis as the preposition. I would translate it, "Be baptized on account of the remission of sins" (with that as the basis for the baptism, in other words). A simply solution for what is a simple Greek problem.
A. T. Robertson points out parallel passages for this usage in his Word Pictures:
"It is seen in Mt 10:41 in three examples eis onoma prophêtou, dikaiou, mathêtou where it cannot be purpose or aim, but rather the basis or ground, on the basis of the name of prophet, righteous man, disciple, because one is, etc. It is seen again in Mt 12:41 about the preaching of Jonah (eis to kêrugma Iôna). They repented because of (or at) the preaching of Jonah. The illustrations of both usages are numerous in the N.T. and the Koiné generally."
A. T. Robertson points out parallel passages for this usage in his Word Pictures:
"It is seen in Mt 10:41 in three examples eis onoma prophêtou, dikaiou, mathêtou where it cannot be purpose or aim, but rather the basis or ground, on the basis of the name of prophet, righteous man, disciple, because one is, etc. It is seen again in Mt 12:41 about the preaching of Jonah (eis to kêrugma Iôna). They repented because of (or at) the preaching of Jonah. The illustrations of both usages are numerous in the N.T. and the Koiné generally."