To restrict what classes are allowed to be used with the template (so assumptions in code can be made about the interface all template variants will share) I propose to extend the synctax of templates from

class MyTemplate<Class T>

to

class MyTemplate<BaseType T>

which would be the equivalent to c#'s class MyTemplate<T> where T : BaseType

It should not introduce any new syntax parsing-wise and does not break existing use where people just have set the default to Class for now.

EDIT

I appears that this should generally work already but only if the restrictive type is part of a lower script module. So maybe this is a bug?

class TemplateRestriction
{
}

class TemplateTest<TemplateRestriction T>
{
}

Returns Bad type 'TemplateRestriction'