Maybe you would first have to look at the platforms that have been trying to compete against Bitmex. The likes of Bybit, PrimeXBT, Deribit and then you will get answers to some of your thoughts.
Your biggest challenge will be trying to get decent volumes to your platform which makes trading experience exciting for most traders. Many have tried and failed. Bybit has improved in that field so far.
Deribit and Bybit for example are no cheaper than bitmex. They have a 0.075 take and 0.025 maker rebate just like bitmex.
Not much an incentive to switch in that case bitmex is king if you are going to pay the same fees.
Our fees would be 3x cheaper and only really trying to cover expenses of running the exchange not excess greed.