Cool.
Given the 99% restart required case for the plugins off this forum anyways and the downsides of users being given some fairly nasty & obscure error messages like the above I like your decision. If they really don't want to restart right then (like when updating several plugins sequentially in plugin updater) they can still click on the "Don't restart" button on that dialog.
Users do tend to just blow through warning message dialogs and forget - heck I've even caught myself out the odd time. Whereas the conveience of that modal choice to restart straight away just makes it a no brainer really.
Are you happy to make the change yourself in both places? Or do you want me to do a plugin updater patch after you do the load plugin one? They both have similar code at the point of plugin installation (but it is replicated).