Maybe you don't have the solution for cabinet loading, but you've stumbled upon a way to do some signal boosting/shaping and that's still pretty cool. I sometimes play around with the DI a bit during reamps using some EQ and Tubedriver or some plugin that livens up the signal more/makes it more "active" than your basic guitar in dry signal. I've never been able to get it "on the way in" like that to see how it actually feels though, but I've made impulses with it after the cabinet. Not quite the same.

You also have perhaps a real time saver, an opportunity to set a pre-eq that works across the board for presets made for other guitars or something.

But really all we want is to switch cabs, I feel your pain. But I finally broke down and got the EPSi IR loader. For the same price, I probably could have gotten another sound card so it would handle the input monitoring, but who knows what kind of issues would happen with latency and such with that configuration. The EPSi is pretty amazing, I've made some 5 second cabinet IRs with reverb tails and stuff that would bog down my recording software for sure, and there's no latency. That's well worth the $200.