Here's a suggestion. Property names for numeric information seem to be on the table -- these should be viewed systematically not haphazardly.

If all text properties had a "dotted" lower-case name, life would be simpler in SMW land all around and maybe Wikidata land too. All page names have an initial capital as a consequence of requiring all text properties to be named with an initial "period" followed by a lower-case letter. The SMW tool mandates the properties from which all derive: .text, .string and .number are basic (along with others like .page). Then, strings have language-based subproperties and number expression subproperties, and numbers have XSD datatype subpropertiess, which in turn have SI unit type subproperties, and so on.

Here's a "Consolidated Listing of ISO 639, ISO 4217, SI Measurement Symbols, and World Time Zones" [1] to illustrate that it is possible to create a unified string- & numeric-type property name dictionary across a wide swath of the standards world.  The document lists a few overlapping symbols then re-assigned to another symbol.

Adopting a "dotted name" text-property naming convention, can segue to easier user interfaces too for query forms at least plus impacts exploited by an SMW query engine. What is meant by these expressions seems pretty natural to most people:

  Property: Height - the value is a wiki pagename or objectname for a "height" numeric object
  Property: .text - (on Height) the value is text markup associated with the Height object
  Property: .string - (on Height) the value is text non-markup data for the Height object
  Property: .ft - (on Height) the value is number of feet associated with the Height object
  Property: Height.text - the value is text markup associated with an anonymous Height object
  Property: Height.string - the value is a "string" property of an anonymous Height object
  Property: Height.ft - the value is a "feet" property of an anonymous Height object

[1] http://www.hypergrove.com/Publications/Symbols.html