You basically have the same feature requests as me.
I decided to just host my personal email through google apps, but an option you can do is this.
1) host your email through google apps (or godaddy).
2) create email address and set to forward to your mobileme address.
3) also in google (or godaddy if possible) set it to delete or archive the original message.
4) Setup the @me.com and @yourdomain.com address on your phone.
This way you can receive the push emails from your phone and also reply from your custom domain. With google I like the delete or achieve feature of original message. That way you won't receive duplicate messages on both accounts. When replying you can select the address to reply from.
Another option if you can't set original message to archive or delete is to just setup your @yourdomain.com address and set that account to only check manually. Then just login now and then and delete the inbox messages.
That would pretty much work, but me like you who uses hosting, scripts, etc.. MobileMe wasn't worth it.
Don't think you can change the send server settings for mobileme but someone else can confirm for u
Thanks for the reply. Sounds like a good way to do it.
Actually I did a little more research on it and tried this out on a MobileMe test account:
get my gmail forwarded to my MobileMe account as you did. Then I took a look at my iphone's MobileMe account settings. Look at the smtp settings and select Add Server.
Then fill in your gmail smtp or whichever your email service is with.
Do the same for Mail on the Mac's MobileMe account.
I tested it and it works great! Mail appears to come from that email instead of MobileMe.
The only thing is that when you're composing message it still shows your MobileMe in the From area but it is indeed being sent from the other smtp server.
What I really love about it is that your email appears in both Mobileme Sent mail as well as the other address's Sent mail.
So all I need configured on my iPhone (and even the Mac I suppose) is my MobileMe account.
So now I can have all the other cool features of MobileMe and still use it's email.