How to route dynamic PPPoE prefix delegated IPv6 prefixes to a layer 3 switch on IOS XE

Question

Network setup:

IOS XE 16.x --> Cisco 3560G layer 3 switch --> clients

The IOS XE device does PPPoE dialing to our ISP and runs some VPNs to other sites. The 3560G does inter-VLAN routing and have a default route to the IOS XE device.

The ISP recently enabled IPv6 and a /56 can be acquired via PPPoE PD. Here is my setup:

interface Dialer0
 ip address negotiated
 ip nat outside
 encapsulation ppp
 ip tcp adjust-mss 1452
 dialer pool 1
 dialer-group 1
 ipv6 address dhcp rapid-commit
 ipv6 address autoconfig
 ipv6 enable
 ipv6 dhcp client pd pppoe-isp
 ipv6 dhcp client request vendor

And we use our own IPv6 prefix in the VPNs. Announcing our own prefixes to the ISP is not an option. Now I want the clients to have native IPv6 access to the Internet, is there any way to achieve this?

My first thought is to allocate a fixed IPv6 prefix to the clients, then use NAT66 (NPTv6) to change the prefixes depending on which interface they are going out, but IOS XE doesn't support NAT66 when the outside prefix is not fixed. Another workaround is to use a script to dynamically change the config on the L3 switch, but this seems to be a bit dirty.