Context

I may have missed a simple way to achieve what I need without modifying ikiwiki, so here is the context.

I have a first-level directory (called bricks) containing a bunch of wiki pages :

/bricks
 |
 |- bla.mdwn
 |
 |- bli.mdwn
 |
 `- ...

I have two groups of tags called direction and usage, stored in two sub-directories of $tagbase :

/tag
 |
 |- direction
 |    |- d1.mdwn
 |    |- d2.mdwn
 |    |- ...
 |
 |- usage
 |    |- u1.mdwn
 |    |- u2.mdwn
 |    |- ...

Any page in /brick can be tagged with one or more tags from any of these tags-groups.

I need to present different views for these wiki pages, so a /view tree is dedicated to this mission :

/view
 |
 |- dev
 |   |- d1.mdwn
 |   |- d2.mdwn
 |   |-...
 |
 |- howto
     |- u1.mdwn
     |- u2.mdwn
     |- ...

... where e.g. /view/dev/d1 lists a subset (depending on other tags) of the pages tagged d1.

My current plan is :

thanks to the pagetemplate plugin, /view/dev/* and /view/howto/* would be assigned two custom templates, containing respectively [[template id=dev_direction]] and [[template id=howto_usage]]
/templates/dev_direction.mdwn and /templates/howto_usage.mdwn would use [[!map ...]] directives to build their views

My issue

Such map directives would look something like the following (more complicated, actually, but let's focus on my current issue) :

[[!map pages="bricks/* and link(tag/usage/<TMPL_VAR BASENAME>)"]]

Where BASENAME value would be, e.g., u1 or d2, depending on the page inserting the template. But BASENAME does not exist. I found that <TMPL_VAR PAGE> is replaced with the full path to the page, but I did not found how to get the page's basename in a template included with a [[template id=...]] directive.

Any idea ?

I guess it would be possible to provide the templates inserted by the template plugin with more TMPL_VAR variables, but I don't know ikiwiki codebase well, so I don't know how hard it would be.

I sure could write a ad-hoc plugin that would use the pagetemplate hook to add a custom <TMPL_LOOP> selector I could use in my templates, or another one that would use the filter hook to add the needed [[!map ...]] where it belongs to, but since ikiwiki's preprocessor directives already almost do what I need, I'd like to avoid the ad-hoc plugin solution.

(Adding a parameter such as name=d1 in every /view/dev/d*.mdwn and /view/howto/u*.mdwn page is not an option : there may be quite a few, that's why I intend to use the pagetemplate plugin in the first place to assign them a common template.)

More or less OT: I've not checked the compatibility of pagetemplate and template plugins yet; can a template (*.tmpl), assigned by pagetemplate, itself call a template (*.mdwn) managed by the template plugin ? The hooks call order tends to make me think it is not possible, which anyway would ruin my current plan.