This should probably be considered along with this idea:

https://apex.oracle.com/ideas/FR-4011

Idea Summary
One of the main reasons us devs and our customers love Apex is how quickly we can prototype something and get our ideas in front of decision makers.

Today I exported my working copy 154 of main app 1000.  I have changed parts of the app whilst other devs are building other areas.  I want to get this in front of our managers today yet i want my working copy only.

When I import 154 into our testbed environment and set the app id to 1000, running the app leaves the url at 1000154 and not 1000. This causes all our existing security and login flows to render the app useless.

Use Case
As a developer

when I import my working copy and set the application id

Then apex can recognise this scenario and offers me the option to set this app as main.

The end result is that the url has app 1000 and not 1000154.

Preferred Solution (Optional)
I suspect a simple checkbox on import would suffice.