I understand your perspective, you want to fully use a product you have paid for, with all features. But if you want to trade crypto, wouldnt it be much easier and rational to do this with a broker who actually offers these kind of products, and not with a broker who explicitly offers only futures trading ?
Most platforms offer much more than what most brokers can make use of. Sierra Chart supports Level 3, but not all brokers support this. With most platforms you would be able to trade japanese futures, but many brokers dont offer them. You will always be restricted by what the broker is offering you. The platform sets the infrastructure, but there is no law or obligation that the broker hat to enable all features for every trader. Quite the opposite. Features often have to be deactivated by the broker for regulatory reasons.
I would not overcomplicate this thing. If you want to trade futures, go to a specialized futures broker and use their expertise. Want to trade stocks ? Go to a broker like Lightspeed, this is their domain. And if you want to focus on cryptos, try to get support from a broker/ company that is renowned for their knowledge and service in these kind of markets.