Output array data on drush error when showing stack trace
You can use XDebug PHP extensions with the following suggested settings:

xdebug.default_enable = 1           ; bool: The stacktraces will be shown by default on an error event.
xdebug.collect_vars = 1             ; bool: Gather information about which variables are used in a certain scope.
xdebug.show_local_vars=1            ; int: Generate stack dumps in error situations.
xdebug.collect_assignments=1        ; bool: Controls whether Xdebug should add variable assignments to function traces.
xdebug.collect_params=4             ; int1-4: Collect the parameters passed to functions when a function call is recorded.
xdebug.collect_return=1             ; bool: Write the return value of function calls to the trace files.
xdebug.var_display_max_children=256 ; int: Amount of array children and object's properties are shown.
xdebug.var_display_max_data=1024    ; int: Max string length that is shown when variables are displayed.
xdebug.var_display_max_depth=5      ; int: How many nested levels of array/object elements are displayed.
xdebug.show_mem_delta=0             ; int: Show the difference in memory usage between function calls.
xdebug.show_exception_trace=1       ; bool: Show a stack trace whenever an exception is raised.
xdebug.max_nesting_level=256        ; int: Controls the protection mechanism for infinite recursion protection.


Since you're experiencing Exception type of error, enabling show_exception_trace will show a stack trace whenever an Exception or Error is raised (even if this Exception or Error is actually caught, so you can always disable it). Enabling collect_params, will display the parameters passed to functions when a function call is recorded (including content of the arrays).

See: Xdebug documentation page.

To verify your XDebug settings from CLI, run:

php -i | grep xdebug