Hello Matko, please correct me if I am wrong but it sounds like you need ability to group VMs (guests) instead of ESX hosts?
Also, please let me know if you have Virtual Center, or all of your ESXi hosts are standalone?
We will be releasing major update (4.0) in about 1 month, even more really cool stuff there. Some new features specifically aim Linux systems that you seem to rely on heavily
infortunately, architecture-wise nothing is changed and it still requires Windows to run. But your request has been noted.