Is it me, or are you not contradicting yourself a bit? You prefer "brighter the better" stainless strings, but now want less brash and subtle nickels? And, why are you dead set against flats? Flats can sound like everything from bright stainless roundwounds to completely dead old school flats, dependent on the brand and construction. They also don't have to feel like bridge support cables (Chromes)… they can be supple, and smooth as silk (LaBella LTFs).
I say all this because I despised flats for 32 years, and only played stainless rounds. I should have tried more than just D'Addario Chromes!! But, now (thank God for Covid boredom) I have tried almost every type, and play nothing BUT flats. They just feel too good, have no string squeak noise, and I don't have to worry about wearing down my fretwire.
Try some EBMM Cobalt flats 40-95 or 45-100 or 105, dependent on how tight you want them to feel. If you don't think they sound bright enough for you, sell them in the classifieds.