Let's try to focus on heating iron block shall we? How can we make it more benefital? Should the heated object be heated for a very very longer time, such as 2 hours or 59 minutes? Should it be used for farms/trap contraptions as a replacement for cactus?
Well for the sake of the question and thread, I'll respond.
For starters, maybe heated metal blocks (iron, metal, maybe even diamond and emerald) should emit particles that allow it appear as if it's "glowing" A redstone particle that's colored orangey-red could work, or a fire particle, though I'm more comfortable with the former.
What it should be used for should be up to the player. When it comes to it being beneficial, well, fire can only be so beneficial through a caveman's uses. Maybe it a heated iron block could in turn, keep any adjacent furnaces ignited and cooking food? Maybe any uncooked food could be cooked on the heated iron block? That's about all of the "benefit" that a heated iron block represented by particles could give, because particles can't emit light.
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In my honest opinion, I don't think this'll be accepted, not to be pessimistic. I remember a thread about FireBlast scalding water and doing half a heart of damage to anyone in a 2 block deep water radius, and it got denied. This is a bit different, so who knows, ANYTHING can change here on PK with the staff team.