Next to the history button in the software centre there could be "Installing windows software" button. When pushing it the user would get three things: information about which are Ubuntu alternatives for windows software (has been proposed before on this site), explained option to use CrossOver and some integrated functionalities of the wine front-end PlayOnLinux. The first section would give information on the most popular Windows software and its alternatives (MS Office and LibreOffice, Photoshop and Gimp, and etc.). The second would explain what is CrossOver, why it is needed and guidelines how to set it up (a button would be even better). Also using virtual machine could be introduced under this section as the common nominator is the “things that solve your problem in exchange for money”. The third would provide user with a free functionalities based on PlayOnLinux. The last option could be accompanied with a message that Ubuntu team advices people to use software from Ubuntu repositories and that the Windows software might not work as well on Ubuntu as it does on Windows. The key is to present the information well and improve accessibility to functions and the right place to do it in Ubuntu is the software centre.
Playonlinux enables to install impressive list of Windows software easily by user just choosing the programme/game from the list and inserting installation media if needed. Some work well and some not that well- the information about that is shared by the community and is visible to user when s/he browses the list. I know that it is not always that rosy experience as I might make it sound but it is a half empty glass and that is a lot for a thirsty.
For an example Ubuntu could at first choose few PlayOnLinux scripts that already work and in return contribute a bit to the development of those scripts how they can. PlayOnLinux would benefit as it would enable to grow their community.
The idea is not that the Windows programmes should be installed the same way and as easily as the ones from Ubuntu repositories. The idea is that software centre would be a right place where to provide such information and where to integrate already existing solutions.