Yes this auto capping or a credit back when using over certain amounts is a fantastic idea. Knowing that I donāt need to plan in advance which bundle to pay for is the key to disrupting the industry. Granted this happens with some of the rollover or credit on your next bill packages.
Being able to share this across multiple people/SIMs is the real disruptor. It would be a bit like buying a family ticket for a days bus travel.
Why not just have tiered pricing? The more you use, the lower the cost per additional GB
The idea of being able to switch between either is great, as some months Iāve got reliable and fast WiFi on demand, yet others Iām stuck on 3/4G
Welcome to the forum! 
How much data do you typically use in a month, with and without reliable WiFi?
Didnāt @nick mention that he couldnāt have bundles across accounts as thereās no profit in there for him if everyone uses it?
Actually - this makes not much sense. EE are offering this to you at X rate. Just charge X rate to customers with 10% markup and regardless of if itās used across the entire account or not you gain profit, right?
We havenāt created these bundles ā theyāre from our direct supplier (not EE) who average them out over their entire customer base, with their own terms attached, e.g. theyāre per-SIM. If we could do them across SIMs we wouldā¦ 
Butā¦ watch this space!
With reliable less than 1gb, without 20-25gb