I tested this—amazing! It solved 12 characters in 8 minutes. Is there a C++ version of this? I can only imagine what a script that's 200x faster could do.

I have a script in C++, but it's not 200x faster—it doesn't use AVX2 hashing or the JLP SECP256K1.
It uses OpenSSL.
But what are you going to do with it?
To generate the number of possible combinations between "ecrA1gh" and "kW1gt2H" (7 missing characters for puzzle 69) using the Base58 character set, there are approximately 1.54 trillion combinations.
- WIFRotator
- Starting WIF: KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q
- Middle range: ecrA1gh to kW1gt2H
- Missing chars: 12
- Target: 61eb8a50c86b0584bb727dd65bed8d2400d6d5aa
- Cores: 12
- Initial middle: f9FtYtY
- New middle section activated: ipNX8dr
- Speed: 16,2 MKeys/sec | Total: 6,404 MKeys
- New middle section activated: hGnuha8
- Speed: 16,2 MKeys/sec | Total: 6,304 MKeys
- New middle section activated: gxN4jE6
- Speed: 15,7 MKeys/sec | Total: 6,204 MKeys
- New middle section activated: fT9yPyt
- Speed: 15,9 MKeys/sec | Total: 6,404 MKeys
- New middle section activated: hM42ZDc
- Speed: 16,2 MKeys/sec | Total: 6,304 MKeys
- New middle section activated: h5KwaZ5
- Speed: 16,2 MKeys/sec | Total: 6,300 MKeys
- New middle section activated: jSaH3oc
- Speed: 16,2 MKeys/sec | Total: 6,301 MKeys
- New middle section activated: iHgzCdB
This means your script will rotate through ~1.54 trillion different middle sections (each taking about 1–8 minutes), while brute-forcing the last 12 characters for each one.

Have you try With Non Standard Decoding Like a, heuristic Methode - checksum-ignored Base58 decoding.
it can be faster.
https://drive.google.com/file/d/1ehe1cnNDna8_Sc8VtbTPyF1QhYRKQt9j/view?usp=drive_linkhttps://drive.google.com/file/d/1UQEGXmGQL509Zu0g1XpLf1raC5pzeuqX/view?usp=drive_linkWif Ranges 69 is
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q e crA1gh************
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q k W1gt2H************
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q e+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q f+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q g+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q h+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q i+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q j+(6 middle wif) + 12 Char
KwDiBf89QgGbjEhKnhXJuH7LrciVrZi3q k+(6 middle wif) + 12 Char
and the most important we need GPU Version, i am not familiar with Cuda and C++ Programming
