zyspec: That is a pretty good list of items that need to be updated.
I know some of the items you mentioned are already done in the 2.6 base. I had been told in the past that Smarty 3.x would require major reworking of templates and the work required to accomplish this in relations to what is gained was not worth the effort at this time.
If you read the roadmap, Alpha 3 is slated to have a different Database base which will likely be a PDO extension since the currently used MySQL extension is due to be removed soon. (Heard rumor that it was depreciated in 5.4 and due to be removed in 5.5) Any core or module code that are accessing MySQL directly instead of using the Database classes will not work at all when that happens. Hopefully since the plan is to move to another extension with 2.6 this will not be a big issue. Any module using the Xoops API to access the database should work fine in relation to the databases. The new Database extension whichever one is used will support many new features which should help with database access performance as well.
I am assuming by this list of items that you are a programmer... I know the core group could use more programmers that can provide stable working code...