Can I use a token to specify the name of an email I want to send?

You could use the My Token with the correct and FULL email name.

My big question is why do it this way? Engagements are designed to prevent the lead from receiving the same email twice automatically. I know some folks had some issues with previous Programs having sent emails to same leads, so if that's what you're doing, then that makes sense.

Keep in mind that your Programs will run independently of the Cast Cadence, so it might be that you end up stacking a bunch of emails on the lead if you don't space your Program wait steps and Casts correctly.

The purpose of doing it this way is to StreeeeeeeeetcH out my content.  I have pretty thin libraries right now so I don't want to burn through unopened content when I can re-gift it by wrapping it in a new subject line.

Starting out, you get Email 1
Next cast:

• If you didn't get email 1, send email 1 (failsafe).  
• If you didn't open email 1, send Email 1a.  
• If you opened Email 1 or 1a, send Email 2.  
• Default: Email 2.

Next cast:

• If you weren't sent 1 or 1a, send 1 (fail safe)
• If you were sent 1a, Send 2
• If you Opened 2 or 2a send 3
• If you Didn't Open 1 send 1a
• Default 2

Next Cast:

• If you weren't sent 2 or 2a, send 2 (fail safe)
• If you were sent 2a, Send 3
• If you Opened 3 or 3a send 4
• If you Didn't Open 2 send 2a
• Default 4

Next Cast:

• If you weren't sent 3 or 3a, send 3
• If you were sent 3a, send 4
• If you opened 4 or 4a, send 5
• If you didn't open 3, send 3a
• Default 4

I want to utilize this for 5 different nurture programs and I want to normalize by storing the value of the Email name in a token (I just used 3rd Normal Form.  Can't argue with 3NF).  

Since the logic I listed above uses the name of the email more than 1 time, I'd like to store that as a token so it's in one place should I want to change it.  Let's say that Email 1 is no longer valid and it's now actually Email 10.  Let's say that we find that Email 3 works better as Email 5.  I can re-write them easily as token.

{{my.Email 1}} = "Email 1"
{{my.Email 1a}} = "Email 1a"
{{my.Email 2}} = "Email 2"

This is about being able to recylce unused content.  Let's say that Email 1a has a better open rate than Email 1 and now I want to swap the order...I can do that easily by re-writing the token.  The program itself never needs to be touched.

OK, short answer: not possible.  When I try this, Marketo crashes when I go to the Schedule tab.  I think this is a bug.