Giving options to a both class and subnet

[Phil Mayers]

Our DHCP config has a bunch of variations of PXE options. There's a 
global / top-level default and some class/subclass overrides, like this:

if substring (option vendor-class-identifier, 0, 9) = "PXEClient" {
         filename "blah";
         next-server ...;
}

class "other" {
         match hardware;
         filename "pxelinux.0";
         next-server ...;
}
subclass "other" 1:fe:ed:de:ad:be:ef;

I've had a request to add another override which applies to all members 
of a class *and* a bunch of subnets by default. We stick all the subnets 
in group{} blocks, so I could just reproduce the options at the top of 
the appropriate group, but it seems a bit messy.

Is there any easy way to make a class apply to a group of subnets as 
well as by "match hardware"?