If they have the wallet identifier, you can use BTCrecover to get the wallet.aes.json using a script to download it, and then use btcrecover as well to brute-force the password using the 90% of the password they know.

BTCrecover (original)
https://github.com/gurnec/btcrecover

BTCrecover fork using Python 3 instead of Pyhon 2 that the original one uses, i have been using recently, seems to have some additional blockchain.com support.
https://github.com/3rdIteration/btcrecover

The script to extract the wallet file, is in the extract-scripts folder called download-blockchain-wallet.py and then use the btcrecover.py to actually password-guess the file.

If you need any help installing/setting up the program, let me know and i will give you a hand best i can but if you follow the readme you may have some success.