I have so many 5* items to heat, and nearly no radiants to level them up with. I could do SL (which guarantees a great supply of Radiants), but I can't collect the crowns needed to aquire 1600 energy each and every day (due to a limited time of gameplay). My idea (one that would support Legendary-Kid's proposal to an extent) was to make it easier to find Radiants, but still keep it rarer than Shinings.

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My idea would be as followed:
Depth 19-22 - In Elite Difficulty, there is a 5% chance for Radiants. This means 95% found will be Shinings, making it hard to find here.
None can be found in Normal or Advanced Difficulty

Depth 24-27 - In Elite difficulty, there's a 25-45% chance for Radiants (more found in deeper depths). Basically, Shinings would still be more common in Depths 24 and 25, while by Depths 26 and 27 the Radiants become almost as easy to find as Shinings.
With Normal, the odds for Radiants are 5-10%, while in Advanced it's a 15-25% for Radiants.

Depth 28 - In Elite Difficulty, there's about a 70% chance of Radiants. It'll be the most common spot for Radiants outside Shadow Lairs. There's still about a 30% chance of Shinings, so your not guaranteed a floor filled with radiants, but you'll have a decent haul.
In Normal, odds of finding Radiants are around 25%, while in Advanced odds are about 50% to find some Radiants.

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By doing this, it gives more time-limited players (like me) a chance to find a few radiants each day, without making them too common that it starts to repeat the events that happened before the recent "fire crystal/orb of alchemy finding ratio" patch (where Radiants were too abundant).