I conclude that you are either looking for a webwallet because you do not realize that you can always use personal bitcoin wallets for online payments, or to conduct transactions in a variety of cryptocurrencies, not just Bitcoin.
You conclude wrong, I deal a lot with payments and most customers have moved away from BTC while my main funds are in BTC, dealing with 10-15 hot and cold wallets as I also need liquidity available would be impossible to manage and would only lead to a mistake sooner or later.
Thanks for the clarification. I misunderstood your point. Obviously, you need a specific app or features to process large online payments. I want to emphasize that using webwallets for large online payments is highly risky, as you are vulnerable to all kinds of malicious attempts online. Some of the suggestions from members here may be helpful, even if only partially, so don't hesitate to ask for expert help whenever you need it.