request for advice / building dhcpd infraestructure

[Leandro]

Hello dhcpd users:
Im planning to manage a /17 network using isc dhcpd. I would like to 
briefly describe my plan so I can get any comments/advices  from the list.
My dhcp server will receive requests from approximately 20 relay agents 
from 3 different access technology.
I dont know in advance behind wich relay will be most ip usage since I 
can not predict witch service will grown over the others.
In order to be able to be flexible with ip pools management, Im thinking on:

     Create a class per each agent.circuit-id
     Subneting the  /17 in /24 subnets
     Create a pool declaration per each subnet.
     Add / Delete "allow members of" statements within the pool 
declaration to bind a relay-agent with one or multiple pool

I also would like to create a default class just in case I can not get 
the option 82 info from some relay-agent, I dont know how to do it yet.
It would be for example with 3 class and 3 pools:

#########################################
class "fth_clients" {
                 match if option agent.circuit-id = "fth_relay";
             }

class "adsl_clients" {
                 match if option agent.circuit-id = "adsl_relay";
             }

class "default_clients" {
                 match if option agent.circuit-id = "";     #need to confirm
             }


shared-network my_pool {
         subnet 1.1.1.0 netmask  255.255.128.0 {

         #1.1.1.0/24 for all clases
         pool {
             range 1.1.1.2 1.1.1.254;
             option broadcast-address 1.1.1.255;
             option subnet-mask 255.255.255.0;
             option routers 1.1.1.1;
             allow members of "fth_clients"
             allow members of "adsl_clients"
             allow members of "default_clients"
         }

         #1.1.2.0/24 only for adsl_clients
         pool {
             range 1.1.2.2 1.1.2.254;
             option broadcast-address 1.1.2.255;
             option subnet-mask 255.255.255.0;
             option routers 1.1.2.1;
             allow members of "adsl_clients"
         }

    }
}

###################################33
Any comment / Advice will be accepted,
Thanks!!!
Leadro.