When Rebellion dug out the rights to Battlezone, they announced that they were rebooting the wrong Battlezone game - the Atari wireframe FPS rather than splendid '90s FPS-RTS. They hastily added that they planned a "remaster" of Battlezone '98, but it sounds like that'll take ages.
For now, you might be interested in Warshift [official site], which sounds like Battlezone with an action-RPG edge. It's an RTS where you build bases and armies but can also slip into units to fight on the battlefield yourself, then level up and customise them too. It hit Steam Early Access last night. Have a look:
As you see, it's combat across land, sea, air, and space, with tanks, mechs, power armour, subs, spaceships, and plenty of other units. You might remember seeing it back when it was crowdfunding under the name Universum: War Front (I didn't until a commenter pointed it out - thanks CobraLad!).
It looks surprisingly good considering it's mostly the work of one chap. Designer, artist, and programmer Cyril Megem says he's been working on Warshift for three years, and is launching it onto Early Access now it's playable - though still incomplete. Megem says "The game will remain in early access development as long as it needs to reach its full potential," so it's probably not one for people without patience - especially given it's just him. As ever, I'd recommend you not buy an Early Access game unless you'd be content with it staying as it is.
Warshift is £14.99 on Steam Early Access. WARSHIFT? WARSHIFT! WARSHIFT WARSHIFT etc.