Not being able to add a tablet to the plan is the only thing keeping us from joining visible. Our child uses the tablet for therapy and is very important tool for us.
Why not add a tablet option? Let's say I have 3 people on my party pay (treat it for a moment like a traditional family plan from a major carrier) for 90 dollars for 3 lines. I'd be completely willing [and eager] to pay an extra 10 dollars to add data only for my iPad. Just enable it to be another unlimited line. The fact that the tablet itself would limit talk & text should be nearly irrelevant. I'd say that doesn't add any complexity at all for non-tablet customers, and most tablet users are savvy enough to understand that trade-off.
Two More Business Cases (for the market analysts):
1 phone + 1 tablet = $35 x2 [assuming you're going solo on the party pay] = $70 [a little pricey, but still beats most big-box carriers]: the customer wins because it's still way under the over $100 Verizon or T-mobile would charge for the same deal, and Visibile wins because it gets the revenue of an additional full line for only an increase in data bandwidth.
Two turtle doves buy a tablet: 2 phone lines + 1 tablet = 30x3 = $90 [again assuming they are in their own party pay group for whatever reason, that's equivalent of the two phone lines for a total of $70 and the tablet added for $20]: Last I checked 20 dollars was about the minimum you'd expect to pay for an unlimited data tablet add on at a major carrier, so someone with two phone lines that's happy with Visible's service should be fine with that arrangement, and since Visible has set the floor price for unlimited talk+text+data for a phone line at $25, 3 lines (one of which is data only) for $90 should still be a win for them.
Sorry for the long-winded post; it's the occupational hazard of being a data analyst...