The Elf class levels are set up to match that of the Arcane levels with +125xp added to each level, so that Elf 1 = 750xp, which is 125xp more than Arcane 1 = 625xp. There is the rule that if an Elf class takes any levels of Arcane then they get a 125xp rebate. However, there is an exception to how the Elf class levels are costed. Elf 4 costs 2500xp, the same as Arcane 4. Some of the examples (but not all) in the Player's Companion show that the Spellsword is created using Elf 4 and no levels of Arcane. Using the table as is, this allows the spellsword to be created with the correct xp cost even without the 125xp rebate that would have come with taking a level of Arcane. This might seem like a moot point.
However, it occurs to me that I could build the Elven Enchanter using Thievery 1, Elf 4 and no levels of Arcane. The xp cost is the same, however using this method seems like it would result in the class using the Thief progression for saving throws and proficiencies (due to racial classes not being used to calculate saving throws), which seems superior to the mage progression in these categories.
Should Elf 4 be repriced to cost 2625xp so that it follows the pattern of the other Elf levels? This would seem to force the Enchanter to be built with at least Arcane 1 (and thus giving it the Mage progression for saving throws and proficiencies) in order to retain a base xp cost of 2700xp.
If the Enchanter was created using even as low a level of Arcane as Arcane 1, should not it have only a prerequisite for INT per the custom class build rules, since Arcane 1 trumps Thievery 1? (Understanding that CHA could have been added per the rule stating "Additional requirements or prime requisites may be imposed by the GM if he deems it necessary for balance or class flavor."
On a side note, in light of the rules for creating custom magic types in Axiom issue #1, should a cap on the levels of Elf+Arcane being set at 4 be considered? When Divine and Inherited magic exceeds the base level (2 for Divine, 3 for Inherited) their xp costs increase geometricly as they grant a number of spells above 100% the norm. However, the progression for Arcane remains flat as the rules are written currently.