IPSEC 1:1 Nat with overlapping networks

Hi Peoples

with new utm 9 there is newly support for 1:1 Nat but no description.
We have a new client side which has the same network like HQ see below. We have no direct access to Clientside Firewall.

HQ Side Lan:
10.0.0.0/24 <=> Public IP (IPSEC)
Client side Lan
10.0.0.0/24 <=> Public IP (IPSEC)

I would like to nat the Client on HQ side to something like 192.168.99.0/24
it is no solution to do the nat (DNAT/SNAT) for every single host, because we have about 80 Clients/Server on each network.

Thx & Regards