2000 Rx300 Stereo Deck Upgrade

[liqrsicc]

Im in desperate need of help for this. I have a 2000 Rx300 with the pioneer system, no nav. I've been searching online for months trying to figure out how to change the factory deck with an aftermarket one. As far as I know I cant because the factory deck also controls the climate. Ive tried a handful of "car audio specialists" but none would consider doing any custom installations or find a kit for one. Has anybody succeeded in changing their deck? Any suggestions to where I can mount one? Is it even possible to add another deck and still have the stock one functional too? Any advice would be appreciated. Thanks!