Thank you for your message however could you specify why do not you like default solution? Such method is widely used in other platforms and systems.
Also there is target="_blank" attribute available in the link of terms and conditions by default. But there is also available a JS code that opens page content without opening it in new window.
That JS is applied for link class mphb-terms-and-conditions-link so you can override function renderTermsAndConditions() and change class to something different e.g.