I've added custom controller under magento frontName and it works.

My routes.xml:

    ...
        <router id="standard">
    
            <route id="customer" frontName="customer">
                <module name="[Vendor]_[ModuleName]"/>
            </route>
    
        </router>
    ...

Path to controller is [Vendor]/Customer/Controller/Address/EditAjax and path in url is /customer/address/editajax. Is there any drawback or possibility of errors with native magento controllers