Client is interested in using Clickonce for deployment and the user population is 40K plus.
Using Clickonce, is it possible to:
For your first question, you can publish your ClickOnce application to several servers and let different user download and update from different server. You can even publish your ClickOnce application from a network file share or from media such as a CD-ROM.
For your second question, you can set the application to update automatically or use the deployment API to manually update your application. For more information, please check the ClickOnce Update Strategy.
More information about ClickOnce, please check:
Hope this helps.