Accessing RDP services via a webtop and SSO

We are looking at using APM to publish our RDS platform. We intend to use SecurID along with AD to authenticate the user into a webtop and to start with we will use the activex / java client. However I am looking to take this further and use the RDP client on the computer following a flow like this below (Image curtsey from http://www.rdsgurus.com/uncategorized/remote-desktop-gateway-pluggable-authentication-and-authorization-sample/))

From reading other posts I get the feeling this is not possible but would like to know if anyone has this type of solution working or if something like this working I would like to hear from you.

If this is something that is not achievable at this time does anyone know if something like this is in the pipeline?

Currently I am being forced into using Remote Desktops is the above achievable with Xen Desktop / VMWare View?

James