Automated transactions are handled by the use of scripts. Scripts are used to automate the execution of tasks. Scripts use variables that hold values which are manipulated using conditional statements, loops and functions. Hence, the implementation of automated deposits and withdrawals of different currencies are handled by scripts
One way is to write software for each cryptocurrency as you suggest.
A lot of it would be reusable code as you can just interface via RPC with your wallets.
Another way is to use a wallet that supports multi currencies and then interface with that wallet.
But lets examine what really is required
those are essentially free as all you need is an ...
Going long USD/BTC is identical to selling the amount of BTC that you have for USD. To put it into perspective, assume you had 1 BTC when the price of BTC was $13,250. When you went long USD/BTC, what you essentially did was you sold 1 BTC and received $13,250 in your account. When the price of BTC dropped to $8,000, you still had $13,250 in your bank ...