If I set up 2FA, only my device can log in. If I become unavailable for some reason, none of my team members can access the account. The only way to do this is for all team members to do the 2FA setup at the same time, which I believe will seed the generator so that they will all produce the same sequence of tokens. But that's just unacceptable. It's like renting an office and only getting a single key.
I find it amazing that in this day and age, most providers still conflate the concepts of "login" and "account". I log into an account; that login is a set of credentials giving me access, but one account obviously must support multiple logins.
Without a clean separation, you turn employees into single points of failure. Shared account credentials is a potential security risk. And it makes it harder to lock out employees who leave the company once given access. And of course, it makes auditing harder because you just have the IP.
Most providers make this mistake: Among DNS providers, I use Gandi, EasyDNS and iWantMyName, all set up like this. Cloud-oriented providers like Digital Ocean and Mailgun, same problem. AWS does the right thing.
You can also add other phone numbers to your 2FA preferences, although I can understand if that's annoying for your colleagues if everyone is getting an SMS on every login.
Could you have people adding multiple phone numbers to the 2FA process and then allow someone to set their preferred, whitelisted number for the SMS?
I need to grant access to a second account to purchase services on my behalf. Does your solution of granting domain modification access work in that case or are we going to have to deal with the SMSes?
Also, is there a plan to upgrade the internal tools that don't much the newer public design? It's pretty jarring.
With the existing 2FA, you can set a primary or disable a number without deleting it. This could work for what you're describing.
It's certainly something we are aware of and multiple logins are planned.
We are using Authy as two-factor authentication service provider and they allow you to use multiple devices: http://blog.authy.com/multi-device