Depends on what the use-case of a locked tab is:
In a web-browser, generally a locked tab is just prevented from closing.
In a file-manager there are a number of different use-cases:
Locked, Directory changes allowed:
1) Do or Do NOT Return to locked folder when a locked tab is activated.
2) Have a command to GoTo Root, where Root is the initial locked path.
+ Allow directory changes within a locked tab, utilizing option 1 or 2.
+ Disallow directory changes within a locked tab, opening a new tab when descending into the file structure.
Opening a new tab, when you attempt to browse above the lock-level to some, seems counter intuitive --- another tab you just have to close.
It is in effect duplicating the tab, at a level above the lock, and only saves a single click compared to just duplicating the tab and going up a level afterwards.
Multi-commander supports some of the options above.