I don't see a need for this if you're using mIRC/DCC/IRC legitimately. The only people I can think of (perhaps not you, but for 98% of the IRC population) that this would come in handy for is people who use mIRC for file trading with XDCC/FServes. This is not the purpose of mIRC.
If you have, for some reason, quite a lot of DCC sessions going you can increase the number of lines of the switchbar, therefore, freeing up some space. Simply go to ALT+O > Display and choose the number of lines under 'lines:' you'd like the switchbar to be.
You can also set DCC windows to be desktop windows, ALT+O > Display > Options > [Windows...] and check the 'Send/Get' box.
My 2 cents.