With the $30,000 borrowed, smart investment in Altcoins can potentially turn your initial asset into $300,000. You could sell the original 1 BTC that you held onto for $100,000 or $150,000. The combined profit from BTC and Altcoins could amount to around $400,000 - $450,000. After repaying the $30,000 borrowed from the exchange, you'd be left with $370,000 - $420,000.
After all this is full of expectation, there's no such smart investment in altcoins, you're only hope the token you invested will going to 10x in bull season.
Assuming the bull season will happen in the next 2 years, if you borrow $30,000 now, you will pay $30,000 + interest rate. Most likely they will use floating interest rate than flat interest rate, so you will pay more especially you borrow for long term.
What if it goes wrong? assuming you will need to pay $35,000 and you lose everything in altcoins, you're use the profit in Bitcoin investment to cover up your mistake.