Gecko would be pointless i think.. We have firefox for that and MicroB are on a custom lighter gecko engine if i remember it right. To get the same performance would be a lot of work and probably impossible. MicroB will not be obsolete soon either. It got pretty good support for html5..

It would be super cool if freemangordon hacked together another browser.. but to be worth it would need some extra feature set we are missing right now.