An espresso-based menu begins with a concentrated coffee preparation and changes the balance through additional ingredients. A latte, mocha and cream-topped espresso are therefore not interchangeable simply because each starts with coffee from the same machine.
Choose the finished drink before choosing its proportions. Consider whether coffee, milk sweetness, chocolate or texture should lead. Measure the ingredients when developing a home recipe so that a change in the drink has an identifiable cause. An espresso blend is a roaster's recommendation for a use, not proof that espresso requires one particular roast color.
Without an espresso machine, a concentrated brewed coffee can produce an enjoyable related drink, but it will not reproduce every feature of pressure-brewed espresso. Adjust the other ingredients to its strength instead of substituting a vaguely defined shot volume. Clear naming and a repeatable recipe make experimentation easier than treating every strong coffee preparation as technically identical.

The conversation
A good question can make a better brew.