Using a third party for micro-transactions is not a perfect solution anyway. Using the Lightning Network looks might seem to be a good solution, but (if I got it right) it requires users to generate invoices for each individual withdrawal, which is problematic. If you know more about it, please let me know.
Thank you!
And what about altcoin withdrawals?
There is an options with almost zero comissions.
It's fast, secure and much easier to implement than Lightning Network - you already have the working structure for altcoins deposits.