There are two reasons why I prefer an arcane warrior to an arcane paladin. First, I want the characters in this hypothetical campaign to have access to the arcane abjuration/evocation spells, not the divine spells. I want them to be damage dealers at melee range with martial weapons and at long range with spells like magic missiles, flaming sphere, acid arrows, fireballs and lightning bolts. I don't want their role to be melee damage dealers/healbots/buffers.
Also, although the paladin's Sacred Oath seems well-suited thematically to the historical vows a knight had to take, I want the characters (be they PCs or NPCs) to retain all their abilities should they decide to abandon/betray the knightly order and their vows.
As for the suggestion of an Eldritch Knight/Wizard multiclass, I want the characters to be able to progress in a single class, and this particular class combination IMO results in too much emphasis on the arcane aspect/progression to the detriment of the warrior aspect/progression. Too much wizard, too little warrior, so to speak.
The swordmage archetype looks interesting, and I'll copy it for possible use at a later time.