You're thinking of infantry fighting vehicles. During the first Gulf War M2 Bradleys destroyed more Iraqi tanks than Coalition tanks did.

> It would run circles around any MBT, easier to maintain, and cheaper.

That's the idea, but in practice lightly armored IFVs were too vulnerable to guerrilla warfare tactics or technicals, so they have mostly evolved to be more like tanks or in some cases literally based on tank chassis.

I mean even lighter than IFVs. Literally something like a Jackal (MWMIK).

War is Boring, The War Nerd or some other outlet expanded upon this idea a few years back. Based on long range desert patrols used by the Brits in WW2, later in Oman, and then in the Gulf Wars. Only works in mostly symmetrical theatres and in specific environments. Hunting Desert Foxes for example.

> too vulnerable to guerrilla warfare tactics or technicals

Yes. Probably not for clearing a Baghdad street. Of course, some genius will apply the same tactics to Urban areas. Because it's cheap and readily available. And see his soldiers shredded. A bit like the Land Rover Snatch.