I have been struggling with this topic for a while. Initially it was the idea that I would let the 360 chips mature, and allow time to get to a stable installer process (defined processes, repeatable steps, low inventory).
The ability to drop a customer once their chip/hack is installed is difficult. It's a psychological thing for the customer (in my experience) - you are their expert, and dropping them with no support will likely leave a bad taste for them, and could spread on forums, websites, etc, thereby killing your business.
Ryu is right, I think - it really is no different with any other mod installation - the chip COULD fry, wire dislodge, whatever. The confidence is solid in the Xbox1 chips. As an installer, you can be confident that there aren't any showstoppers. With the 360, it's still not solidified.
I have got to agree in principle with Heet- as soon as it's displayed in a working state, out the door, then the customer is on their own. I always say: "It's as durable as it was on the day you bought it; and if you treat it like gold, nothing should go wrong."
Warranty labels (tamper evident?) are an excellent idea - what's the cost on something like that?
Emails are slowly coming to me with requests on 'do you do the 360 yet'? The demand is out there, and the naive people assume that the Xbox mod process is stable, surely the 360 modding is stable as well.
I am looking for installers comments on providing flash vs chip, as of today. What's the least hassle for the customer, today? Is Microsoft detecting modded firmwares? Are they being overwritten or bricked?