I do think the Bloodwave Warlord needs some love, but I don't really like any of these suggestions.
-Most soldier cards are already in the War school (and those that aren't probably would not be very useful to him anyway).
-The two-handed weapon change would make him too similar to the Barbarian (one of the next upcoming Mages), who is almost assured to specialize in two-handed weapons and/or dual-wielding.
-Giving him more life, while effective, is boring and doesn't fix his weak abilities.
-Same with mana bonus (which I view as not thematic anyway, since mana control is associated with the Arcane school and the Wizard).
-Paying 1 less mana per turn for war conjurations is the sort of thing which could easily be added as a new ring equipment card effect, but that won't really fix his issues. It will definitely not help his standing in relation to the other Warlord, since any new cards will buff both versions equally.
-Changing the veterans ability is the most promising idea, but restricting it to 2x a creature's level goes against his swarm philosophy. Most of the Bloodwave Warlord's thematic creatures have really poor health and minimal armor. Goblin Grunts have 4 life. Which means that by the time one manages to actually become a veteran (assuming it is not killed instantly), it will die shortly thereafter before it can actually make use of the benefits.
-Once again, this is the sort of thing which would probably be handled with the addition of a new equipment card. I would actually be a fan of this, but at present it wouldn't have a major impact (there aren't that many cards which only effect soldiers) and it wouldn't make him a real competitor to the Anvil Throne Warlord.
Honestly, the only way I see for the Bloodwave Warlord to be properly fixed is for Arcane Wonders to directly errata his card to drastically improve his veterans ability. Any newly introduced cards will only make both Warlords better by an equal margin, and the Anvil Throne Warlord is already far superior to the Bloodwave one. While they are at it, they should probably look at the Priest and Johktari Beastmaster as well. There is little compelling reason to ever play as either of them. I understand the devs' reluctance to errata cards, but sometimes it really is necessary. Having 3 mages be all but useless compared to the rest hurts replayability and competitive diversity.