Franz
Perhaps we should clear up some terminology. Since IPSec is for IP unicast traffic and since DHCP requests are broadcast I believe that the specific technical answer is no it is not possible to transport the original DHCP client requests through an IPSec VPN tunnel to a remote server.
However I believe that it should be possible to configure ip helper-address on the LAN interface of the remote VPN router which will forward a unicast copy of the request through the tunnel to a remote DHCP server. So the result that you seem to want may be achievable.
HTH
Rick
HTH
Rick