since there's a grate you can fall through on the tower and you can't squid for safety, and you HAVE to be on it for it to move forward, you will have to support the person on the tower a lot
defensive strategies like throwing ink walls in spots where the other team has issues getting past and using the bubbler in the area of the person on the tower (assuming you even can, if its like an ubercharge in tf2 youll wont be able to accomplish the objective with it) is going to be essential
the person on the tower HAS to have mobility options for safely approaching and retreating it, and teams will probably have more than 1 player geared toward doing that. i can see the extended mobility the splattershot jr. has in splatterhopping and splatdashing being amazing for this mode, since you have to be mobile to leave firefights you can't win, and this maybe be the gamemode where chargers see the most use for safely protecting the tower-runners