IF your use case is only limited to using your wallet layer (and never try to access those funds from alternate ready-to-use wallets), you can customise your address gap while creating/restoring your wallet when using cardano-wallet API.
Note that obviously this will have impact on performance for searching UTxOs across the wallets, so you might want to also consider splitting user base into multiple accounts and (potentially based on use cases/types) wallets.
The other alternate would be managing the wallet yourself using something like cardano-addresses or cardano-rosetta where-in you can derive and maintain record against users while deriving from same base root key.