I'm feeling the Template name-space is ideal for this. My thoughts will follow this route, but the subnames could go elsewhere I suppose.

I usually work these naming issues out best by brainstorming. So, I'll riff on a few ideas here in a response, and take or leave any of them. Sometimes the reasoning behind one is as useful in finding another one as the possible name itself.

My first instinct was Template::Multitool (I'm a fan of Swiss Army and Leatherman inspired toolsets).

I do like Template::Pluggable, although you're not really plugging the others in so much as accepting their syntax as a layer, are you? Maybe Template::(Multi|Poly)Syntactic makes sense, although it's not the shortest or simplest.

Say, since you're doing multiple Toolkits, perhaps you've built a whole Workshop. Template::Workshop, maybe.

Template::Agnostic perhaps goes too far, but it makes for an interesting name.

I almost want to recommend Template::Berlitz, but I wouldn't want to steer you towards trademark issues. Template::Cooperative works for the aspect that more than one templating dialect can be used together, but not for much else.

Template::Retool is kind of a pun on TT, but it's also serves the notion that a large project may not be able to move from one templating module to another all at once. By using something that accepts more than one dialect, a project can go piecemeal if necessary.

Template::Dialects gets to one of the core features, in that it's different dialects of templating with which the module deals.

There you have my initial thoughts. I won't be offended if you hate any or all of them.