I've seen the 1:72s of the mecha you mentioned on ebay. You're right, waaay too much for my budget as well. Have you thought about the 1:100 versions of those mechs to be closer to the BT "game" scale as opposed to the scale from the original animes?
I also have the Ziyon kit. I'm planning on building it with the Kurita reflective camo scheme from the old MechWarrior rulebook. I'm also looking at using some of my spares of other Macross kits in 1:100 for similar BT projects. After what I read about the lance you want to build, I checked the kits I had handy for size and thought about the BT tonnage stats. First, the stats: Battlemaster-85t, Marauder-75t, Warhammer-70t, Rifleman-60t.
The box for the Ziyon kit says it's 16.5 cm assembled. The size for the Glaug ( BT "Marauder" ) in 1:100 is also about 16.5 cm and would be about 23cm in 1:72. The Tomahawk ( BT "Warhammer" ) is 12.7 cm in 1:100 and would be 17.6 cm in 1:72. I didn't have the Defender ( BT "Rifleman" ) kit handy, but it's about the same size as the Tomahawk. Going with 1:72 for all of them, you'd have the "Lord of the Battlefield" being shorter than mechs 10-15 tons lighter, 25 tons in the case of the Rifleman!
The only kit with visible crew is the Ziyon so you don't have to worry about different-scale visible pilots.