Being able to craft your own fishing rod is something I'd like to have in the game. I've thought of two ways to implement it, but figured I'd ask here if any one way seems preferable to you :)
CRAFT AT HOME, EQUIP AS ONE ITEM
Your character will have a player house in the game with various things one can do there. The house could include a crafting station for working on your fishing rod, where you assemble various components (probably four - rod, reel, line, hook) into a fishing rod. The bonus of this method is that the rod will be a single item that you take with you, equipped into one dedicated slot on your paperdoll, and any extra fishing rods you want to take will take up just one small spot each in your inventory. The con is that when you find shiny new upgrade parts, you'll have to return to your player house to swap them out into your rod.
MIX-AND-MATCH SEPARATE ITEMS
The other method is a mix-and-match job where you have four slots on your paperdoll, one for each component of the fishing rod, and you can swap each individual component out on the fly. The bonus to this method is that if you're fishing in an area and find a new reel that's an upgrade on your current reel, you can swap it out immediately. The downside is that each component is now separate and taking up more space in your inventory, so if you want to save fishing rod 'sets', they'll take up more space.