Well, reclassing is available as soon as you get the consignment shop which sells all the seals at level 1.(Though you can only buy 2 master seals and 1 of the other seals at first until you level it up to max at which I believe they become infinite)
Apparently, you can reclaass at an level you want this time since you don't drop in levels.
As more magic Kamui, it depends on your reclass option which you choose during character customization.I am not sure about the dragon sone thing, just don't make Str your flaw.
Also just saying, Kamui gets magic upon promotion.
so magic is not bad.