What bothers me about this, speaking as an adopted person, is that by adopting the child - they will lose their prior identity.

I don't think that such lengths should be taken, so you will have an easier time with childsupport? Why can't other options (ie, marriage) be taken.
Why does the child bear the brunt of these changes, so life will be easier for you?

This won't have a detrimental affect on the child, you won't be taking away their truth and their real identity. Losing one's identity, is a huge thing - especially if its not in the best interests of the child. Monetary reasons are, in my view, not acceptable reasons to lose your identity.

I would prefer guardianship or similar, but adoption is not an avenue that I would go down when other ways are possible to achieve the outcome you want.