That's not correct, the Deepak class is designed as a fleet tanker with some replenishment capabilities if you want, but the Aditya class for example was designed as a Fleet Support Ship (just what the RFI is looking for), with more storage capabilities for cargo other than oil, or fluids in general and modern FSSs or JSSs, have even dedicated vehicle decks, or even a well deck with amphibious vehicles.
Here is a graphic of an evaluation of the Royal Navy, for support vessels:
It also shows 3 different class of replenishment vessels, although they all have tanker capabilities, but you have the general tanker design, the support ship which can include repair facilities like the Aditha class and a version with amphibious / logistical capabilities (basically a mix between a tanker and an LDP). So depending on what you want, you can gear these vessles in a certain direction, while maintaining the general tanker / replenishment capability.
The general specs and even the extern replenishment mast design will be similar, be it for a tanker or a FSS/JSS, but the internal space will be used differently, depending on the roles. That's why the Brave class will perfectly fit to the RFI here, but why I also expect a JSS offer of the dutch Schelde / spanish Navantia shipyards, based on their Enforcer designs.
However, I am more interested in what our Indian shipyards might offer to this competition:
Garden Reach Shipbuilders & Engineers Ltd :-- Welcome
The Garden Reach Shipbuilders had done it before and might offer a modern design based on their experience, L&T Shipyards might form a JVs with a foreign partner too. Pipavav will for sure come with a joint proposal of DCNSs Brave class, so it will be an interesting competition.