Brand has a lot more damage that's independant of items than Ryze, so he still deal damage on a reduced gold income
Veigars stun is a lot more useful for a support as it can hit multiple people or control a large zone while it is up, it is also a lot safer to use since it has better range, the recent changes that gave veigar AP when harassing in lane and added an execute to his ult also helped his support capabilities
Ryze on the other hand has the ability to root a single target for 1-2 seconds, requiring 2 of his spells to get the full root duration, after that the only thin he has for follow up is his Q, he doesn't really have enough up time on the root to make it worthwile, there are a lot of supports that outclass him in CC and utility as well as a few that outclass him in damage. It would be a lot better to keep him as a top or mid laner, if you do take him bot it might be better to have him paired with a support so he can scale up.