BattleTanx: Global Assault is still fun, despite the fact that it's a bit gray behind the ears. From a graphical standpoint, though, it hasn't aged well at all -- textures are muddy, the models are expectedly poor, and the presentation in general is pretty ugly. Overall, the game wouldn't work very well as a port to the Wii without some seriously heavy modification. But a sequel? Therein lies an opportunity.
With the exception of Battalion Wars II, which received respectable reviews when it was released in 2007, the market is largely devoid of action-based games in the BattleTanx vein. Despite its post-apocalyptic setting, a new graphical style with a little artistic style could go a long way towards making BattleTanx stand out -- just imagine a 3D version of Advance Wars: Days of Ruin, only heavy on action and light on strategy.
It's easy to picture the pitfalls games like this often have -- poor AI, boring level design, and cheap production values are all markers of a quick cash-in action title. But with a smart designer rebooting the franchise, BattleTanx could go a long way as a multiplayer action game. Online combat with at least four people on a team would be fantastic, and the ability to command your allied tanks could potentially add an entirely new layer of gameplay to the series.
A revival on the Wii would also fix one of the most frustrating aspects of Global Assault: its somewhat obtuse control scheme. Like far too many N64 games, the control stick was the main method of controlling both movement and aiming, making it far too difficult to accurately attack someone and dodge their fire at the same time. Any controller with two joysticks could do the job better, but the Wii Remote is an even better choice: while the nunchuk can control movement, turning the Remote from side-to-side could imitate a real tank turret.
3DO's work-in-progress sequel to Global Assault died with the company, but there's still ample opportunity for someone to run with the franchise and bring it back to its former (minor) glory. The genre remains relatively untapped, and a game with a strong multiplayer presence and more of the crazy powerups and environmental destruction that made BattleTanx fun could do well on the Wii marketplace. Until then, we'll have to look forward to the unbridled action of Wii Sports Resort to satiate our bloodlust. Sometimes Wii Play Tanks! just doesn't cut it, y'know?

