Sure, it will work. Why do you need an HLT? You can simply use your kettle as an HLT and hold your initial runnings in a bucket if batch sparging? That's wohat I would do FWIW.
/\.... Thats what I do. I collect my runnings in my bucket until I use all my sparge water then dump into the kettle. Plus you can measure your volumes with the markings..
I did that in the past as well and it worked fine. It really depends on the type of bucket though. If it's the white food grade plastic it should be good. Not sure what the temp tolerance is on them but if it's below 150F then I think you are probably fine.