ARM Template, dynamically assign property tags inside resource, based on parameter value

I have application gateway resource inside ARM template. Now we want to parameterize the gateway tier to user.

Now based on the tier if user chooses WAF, then I need to add the below key value pair inside the resource :

"webApplicationFirewallConfiguration": {
"enabled": true
"firewallMode": "Prevention",
"maxRequestBodySizeInKb": 128,
"requestBodyCheck": true,
"ruleSetType": "OWASP",
"ruleSetVersion": "3.0"
}