The values for this are stored in the registry per user. Below is an example on how to modify the data with SPE.

$ribbonCommands = "{D33A0641-9F1C-4984-8342-0655C3D0F123}|{EDA2F1DC-0412-45B2-9FDD-0700B03F28CB}|{93F6C3FE-B36E-4083-BA48-19DE43F19F49}"
$registryKey = "/Current_User/Ribbon/My Strip"

<#
  Current_User is automatically replaced by the Sitecore API
  Optionally replace Current_User with domain\username if you want 
  to apply to a different user than the one logged in
#>
[Sitecore.Web.UI.HtmlControls.Registry]::SetValue($registryKey, $ribbonCommands)

The values for this are stored in the registry per user. Below is an example on how to modify the data with Sitecore PowerShell Extensions (SPE).

$ribbonCommands = "{D33A0641-9F1C-4984-8342-0655C3D0F123}|{EDA2F1DC-0412-45B2-9FDD-0700B03F28CB}|{93F6C3FE-B36E-4083-BA48-19DE43F19F49}"
$registryKey = "/Current_User/Ribbon/My Strip"

<#
  Current_User is automatically replaced by the Sitecore API
  Optionally replace Current_User with domain\username if you want 
  to apply to a different user than the one logged in
#>
[Sitecore.Web.UI.HtmlControls.Registry]::SetValue($registryKey, $ribbonCommands)

Update

One option to consider is to have a process run either periodically or during login that would ensure the user has the appropriate settings applied. SPE has an integration point for this.

The values for this are stored in the registry per user. Below is an example on how to modify the data with SPE.

$ribbonCommands = "{D33A0641-9F1C-4984-8342-0655C3D0F123}|{EDA2F1DC-0412-45B2-9FDD-0700B03F28CB}|{93F6C3FE-B36E-4083-BA48-19DE43F19F49}"
# Optionally replace Current_User with domain\username
[Sitecore.Web.UI.HtmlControls.Registry]::SetValue("/Current_User/Ribbon/My Strip", $ribbonCommands)

The values for this are stored in the registry per user. Below is an example on how to modify the data with SPE.

$ribbonCommands = "{D33A0641-9F1C-4984-8342-0655C3D0F123}|{EDA2F1DC-0412-45B2-9FDD-0700B03F28CB}|{93F6C3FE-B36E-4083-BA48-19DE43F19F49}"
$registryKey = "/Current_User/Ribbon/My Strip"

<#
  Current_User is automatically replaced by the Sitecore API
  Optionally replace Current_User with domain\username if you want 
  to apply to a different user than the one logged in
#>
[Sitecore.Web.UI.HtmlControls.Registry]::SetValue($registryKey, $ribbonCommands)