I have been using Radmin since 1.0, and I have always liked it above all others. The one drawback is the need for the port forwarding that has been successfully avoided in other inferior products. By inferior I mean slower, since they do have a method where a client can click on a website link, install the server and be helped without talking them through forwarding ports and getting their public ip. Please check out the Bomgar box, this is a nice solution, but also ultravnc, gotomypc, and webex can do it, why can't Radmin. If you have to make security or speed concessions, then so be it, release a different product called wradmin or something. Making it work with the same viewer would be good though. Some of my wireless clients are on a network WITHIN a private (10.10.10.x)network, so port forwarding is impossible.
You guys are way ahead of the curve on speed, but a little behind in this area.
You've put your finger on what is probably the most requested feature for RAdmin. A solution for this (server initiated connections) was originally a planned feature of v3.x, but for some reason it was never implemented. I've heard rumors that something along these lines is planned for v4.x, but I can't confirm that. (Eugene?)
Unfortunately, if past history is anything to judge by, it may still be quite some time before we see v4.x. In the mean time, there are some workaround solutions. Probably the most popular is to implement some sort of software VPN. Hamachi (https://secure.logmein.com/products/hamachi/vpn.asp?lang=en) is one of the more popular suggestions. I also seem to recall EchoVNC mentioned, but I haven't explored the details on that.
BTW, I'm assuming in the situation you mentioned that you don't have control over the 10.10.10.x network that your client is behind. If you do, then you CAN make the port forwarding work with a little tinkering.