Yes Martin, I think the idea of giving a choice of New 'Welcome XXX' is great.
As you have found with Instant Press, it isn't always convenient to make fundamental site features as a plugin. There is little difference in principle between a 'New Welcome' app and the existing appliances. However, I think to qualify as a 'New Welcome' the developer(s) should have some commitment to maintain the code and keep the repo up to date. At present, many of the appliances are out of date and this has reduced confidence in using them.
