Check position of parameters and args.
Un-splittability as property of data member
Exclude the content of ROOT::Meta::Selection a priori to avoid mistakes

of the users, for example combining a selection xml and a dict selection.
Express in a more convenient way the default exclusions
Express non-splittability with a comment ("||")
Introduce recursion to allow recursive template argument removal

if you have something like A<int, B<double,4, float>> you must
know how many arguments you have to skip for B in advance.
Add a factorised infrastructure for template argument name removal

and disable the functionality for not removing template arguments
which are marked to be removed but have a value different from the
default one.
Atlas does not expect this feature and some more coding is involved
since this comparison is not always trivial.
Add more error messages. Make execution faster

reshuffling if conditions.