I don't think the benefits would justify the cost(building and maintenance costs), however I won't lie, the potential benefits are very tempting. After all, who would say no to a flying battle-carrier!?
The railgun's all well and good but remember 12(?) 14" main guns from the Battle-carrier, that's like 1½ bismarck, not to mention 2 supper-carrier decks/hulls.
I can already see it, 14" guns battering the Dwarven magic shields and hull, the expressions on their faces as they see and experience superior firepower at it's finest.
Megan will be utterly devastated when she see everything she did get blown away by the Rail Gun or the Battle-carrier's (relatively) overpowered main guns