adespo: I have never 'bagged' any orchids. Sphagnum moss will not hurt in any way. I don't use much of it for Phals. But wrapping 'rootless' Phals in them have produced some good results for me.It may have been just coincidence. I am sorry I cannot be definitive in my reply since I have very little experience. I am always willing to try
I have bought some commercial mixes (Schultz is one , I think) but I was not happy with them. It seems they have more gravel, stones and rocks in them.
Unless someone suggests otherwise you could go on with your plan. My only suggestion is that you consider making your own mix.
Good luck.