Thanks for posting! You might consider marking your discussion a question for better visibility.
DHCP client on the WAN will add a default route. You may also use static routes, but I'm not sure you can avoid the default route given in DHCP. You could, however, leverage Policy Based Routing (PBR) to override the route table, depending on your scenario. Check out Configuring Policy Based Routing in AOS and let us know if you have any more questions (and how it goes)!
The DHCP client will add the default route unless you specify no-default-route in your configuration. You can also specify the administrative distance. Doing so will allow you to have another static route that could take priority over the DHCP assigned route. See the list of DHCP client options below.
I hope this helps.
class-id - Configure DHCP vendor class identifier
client-id - Configure DHCP client identifier
hostname - Configure DHCP client host name
no-default-route - Do not install the default-route obtained via DHCP
no-domain-name - Do not install the domain-name obtained via DHCP
no-nameservers - Do not install the DNS servers obtained via DHCP
track - Make dhcp dependent upon a track
<1-255> - Administrative distance
Good to know!