Having looked at your original post and the replies you seem to have no idea how Alliances work in the first place. There is more to running an Alliance than an ongoing cost each month and if a group of people want to work together that will just be factored in and if it works well will not be a hurdle to success. If you think that just because this is imposed it will be easier to recruit to your own Alliance that will not happen, that comes down to personality and the ability of the leadership, good leaders make good Alliances.
So if you plan to place any additional costs this will always be easily absorbed by the membership of any Large Alliance so why add needless taxes to complicate administration of a Corps/Alliances assets.
If you had suggested improving the ingame tools to administer Corp/Alliances and even Coalitions I might have had more positive to say about your post.