Can one parameterize Powershell functions in bulk?

I doubt there's a "built-in" way. If you're determined, I can think of a way to do it, though whether it's a good way is highly questionable. You could assign the repeated declarations to a string, then interpolate that string into strings containing the function definitions, and use Invoke-Expression to define the functions from those strings. Example:

RepeatedParamBlockTest.psm1

$declarations = @'
  [CmdletBinding()]
  param(
    [parameter(Mandatory = $true, Position = 0)] [Alias('Egg', 'Yung')] [string]$Foo,
    [parameter(Mandatory = $true, Position = 1, HelpMessage = "Bar must be a multiple of 5")] [Alias('Rod', 'Beam')] [ValidateScript({$_ % 5 -eq 0})][int]$Bar
  )
'@

Invoke-Expression ("
  function DisplayParams {
    $declarations" + @'

    # This function displays the values of the parameters Foo and Bar
    Write-Host
    Write-Host "Foo: $Foo"
    Write-Host "Bar: $Bar"
  }
'@)

Invoke-Expression ("
  function MultiplyParams {
    [CmdletBinding()]
    $declarations" + @'

    # This function multiplies the values of the parameters Foo and Bar and returns the result
    Write-Verbose "Multiplying '$Foo' by '$Bar'..."
    $multiplied = $Foo * $Bar
    return $multiplied
  }
'@)

If you have many functions, you can streamline this by using a foreach loop instead of separate iex statements:

$declarations = @'
  [CmdletBinding()]
  param(
    $foo,
    $bar
  )
'@

foreach ($functiondef in $(
  ("
    function DisplayParams {
      $declarations" + @'

      # This function displays the values of the parameters Foo and Bar
      Write-Host
      Write-Host "Foo: $Foo"
      Write-Host "Bar: $Bar"
    }
'@),

  ("
    function MultiplyParams {
      $declarations" + @'

      # This function multiplies the values of the parameters Foo and Bar and returns the result
      Write-Verbose "Multiplying '$Foo' by '$Bar'..."
      $multiplied = $Foo * $Bar
      return $multiplied
    }
'@)
  )) {
  Invoke-Expression $functiondef
}

Note the following:

• '@ must always be at the beginning of the line (no indentation)
• '@) at the end of each function definition string is followed by a comma for all except the last one, because these strings form an array in the expression part of the foreach loop.

Console session demonstrating that this works:

06-13-14 19:43:31.18 C:\Data Files\scratch\so» Import-Module .\RepeatedParamBlockTest.psm1
06-13-14 20:03:28.56 C:\Data Files\scratch\so» DisplayParams -Foo 'bar' -Bar 8
DisplayParams : Cannot validate argument on parameter 'Bar'. The "$_ % 5 -eq 0" validation script for the argument with value "8" did not return true. Determine why the validation script failed and then try the command again.
At line:1 char:31
+ DisplayParams -Foo 'bar' -Bar 8
+                               ~
    + CategoryInfo          : InvalidData: (:) [DisplayParams], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,DisplayParams

06-13-14 20:03:39.07 C:\Data Files\scratch\so» DisplayParams -Foo bar

cmdlet DisplayParams at command pipeline position 1
Supply values for the following parameters:
(Type !? for Help.)
Bar: !?
Bar must be a multiple of 5
Bar: 25

Foo: bar
Bar: 25
06-13-14 20:03:52.73 C:\Data Files\scratch\so» MultiplyParams _ 50
__________________________________________________
06-13-14 20:04:22.78 C:\Data Files\scratch\so»

It's not something that's likely to be implemented as a feature because I really don't think there's much demand for a "clean" way to do something like this rather than just copying and pasting the parameter list. How often does anyone define a significantly large number of functions with identical parameters? I suppose it wouldn't hurt to allow using a splatted array as a parameter list (as I noted in a comment on another answer, AFAIK there currently isn't any way to use an array), but it would be of very limited value.

In any case, it's an interesting question from an academic perspective. I'm curious whether anyone will come up with a better way to do it.

$declarations = @'
  [CmdletBinding()]
  param(
    $computername,
    $credential
  )
'@

foreach ($functiondef in $(
  ("
    function Get-PhysicalDisk {
      $declarations" + @'

      Get-WmiObject win32_physicalmedia @PSBoundParameters
    }
'@),

  ("
    function Get-Uptime {
      $declarations" + @'

      Win32_OperatingSystem @PSBoundParameters
    }
'@)
  )) {
  Invoke-Expression $functiondef
}

This can be done using a technique called splatting, where your parameters are prepared using a hash table.

To get more information how to do it from the help, run the command

Get-Help about_Splatting