not sure if it has been done already i have not really been keeping up with other's work and what not. we should start thinking about replacing the rendering system in the 317 client if we are going to continue using it. i know there have been large problems with framerates on resizable clients mostly in part due to the software rendering used in the 317 client. i use to advocate the switch to new engine client's if everyone was just going to put new engine features in, but after playing around with the new engine client's i came back to 317 simply because (as we have discussed before old friend) it's what i have used for almost a decade. i also as also discussed keep on writing/rewriting/implementing a user interface component system around the 317 client. as new engine client's handle the ui as well as 'RSInterface's' in a completely different way it would take me a long time to research and learn this new system, and with full time work and what not right now that is not feasible for myself.
this would probably be a rather large and time consuming project and would require a community effort and continuous development. as you said in your original post there has been major progress in the move away from unrefactored clients (remember class30_sub2_sub1_sub1 for RGBImage's haha), which has definitely had a significant impact on rs2#317 client development.