Level both tank classes?

[Bardo]

You should be fine on tokens, just pick which one you want to gear as main. Both can use Darklight, CT, and Allagan gear, so it's really just the myth purchases that will warrant consideration (they do share myth accessories, as well).

But here's the problem I see with that:
If he chooses War as his main and starts to get several i90 pieces for it while being stuck with i70/80 on PLD, is there really any circumstance in which PLD would be "better" while having weaker gear?

In my opinion, having both classes really doesn't add any flexibility unless they're similarly geared.
And if he's in full Darklight and not running Coil, it's going to be a LONG while until he could have both classes in i90.
By that time we might be talking about an expansion and new tank jobs.
So I think in his circumstance it would be better to just concentrate on gearing his WAR.

OF COURSE:
If he's got a ton of free time after capping myth... then there's really no reason NOT to go ahead and level PLD.
In which case I agree with you guys that it would be a good idea.