How to Share an Email Address in Gmail

My wife and I each have our own email addresses. Common, though she is irked by a few friends who don't. They can only be emailed by sending to the joint "family" email, often actually just the husband's name. Trust issues? Anyway...

Having a joint account is handy now and then. I want one. They're good for things like that real estate agent who just can't figure out "reply all", or that web site that only allows one email address to be entered you both want to track.

Bad news, I didn't find a perfect answer. Good news, I found one good enough... only you and your significant other can mess it up, and only slightly:

Set up a new gmail account, have it forward to each of you. Set up your gmail account to be able to send as the joint account when you choose.

Walk through:

• Create a new gmail account wife.and.i@gmail.com by going to gmail when you're not logged in. (or use an incognito window in chrome)
• In Settings/Forwarding, add forwarding addresses for your existing accounts, wife@gmail.com and me@gmail.com
• In Settings/Filters, add a filter to match everything. This is a tad tricky, you can't just use From: *. So, create a filter that Doesn't have: some_long_random_string_sldkfjslkdjfsdfkjsdf and then select one account to forward to. Repeat, creating a new filter, for the second account.
• Configure your personal account (me@gmail.com, repeat for wife@gmail.com) to be able to send and reply from the joint account.
• in Settings/Accounts in the "Send mail as:" section, add wife.and.i@gmail.com
• On the same page, select "Reply from the same address the message was sent to"

It works: 

• Easily give the shared email address wife.and.i@gmail.com to anyone and you'll both receive the emails in your personal accounts without needing to ever log into wife.and.i@gmail.com again.
• Replying to an email sent to the joint account will "just work" and appear to come from the joint account. (But, don't forget to CC your significant other if you want them to see your reply)
• Writing a new email as if it came from the joint account is easy too:
• Compose a new message, above the To: is the From: address, and you can change it to the joint account.
• (But, don't forget to CC your significant other if you want them to see your reply)

What's tedious is that you must remember to CC your other every time. Now, we're all high and mighty about external people who can't remember to reply-all, so we should be able to remember to CC everyone each time, right? Still... tedious. If you forget, at least the reply from the external people will go back to both of you.

Here are the other things I tried:

• Create an outgoing filter to automatically forward to your significant other's account?
• Nope, you can filter outgoing email (adding labels, say), but you can't forward them.
• Create an outgoing filter to label and remind you that you forgot to CC?
• Nope, you can add a label, but not send it to the inbox also or mark it unread, so no way to get attention.
• Create a group on googlegroups.com?
• Nope, you can send and reply as the shared email, but you must manually CC your significant other's account each time. The group account doesn't appear in a reply all because you're sending as that account. If you're not sending as that account it works, yay, but then you're sending as just you, and replies will not go to the joint account.

Have a better solution? Lemme have it in the comments!