I have a road bike (Orbea Aqua T23) on which many of the components are coming to the end of their lives. As such I'm replacing most of them, and was wondering what people thought were good mods to make to a road bike to make it best suited for commuting? Thanks!!!
As the comments say, if you're more specific, people can help you better.
That said, some general advice for a commuter bike:
Sturdier tyres, as wide as you can get away with in your frame. Ideally with puncture protection.
Fenders / mud guards. Can be had as clip-on, in case your bike frame doesn't support permanently mounted ones.
Lights. Essential. Here's where more information would be useful. If you have to replace the front wheel anyway, look to replace it with one that has a dynamo hub (you might need to ask a shop to build them for you). This way, you don't have to deal with battery lights. Otherwise, get battery lights.
Reflectors, front, rear, spokes. Cheap, and boost your visibility.
None of that, with the possible exception of the tyres and the front wheel, is, strictly speaking, a replacement for existing parts. Still, it's necessary if you want to commute in darkness or bad weather.
As for other replacements, this is mostly a guessing game since you don't tell us what needs replacing. So, in no particular order:
Do you need the front gear shifter? If you can get away with only one chain ring, that's removing one potential source for trouble / extra maintenance. Note that this might necessitate a new crank. Don't know if you need that anyway.
Cheap saddle if you have to park outdoors. Provided you like your old saddle, it's still in good working order, and you can use it better elsewhere.
Hybrid clip-in / flat pedals. So you can wear "normal" shoes for shorter rides, and be clipped in for longer ones. That's assuming you're using roadbike-style clipless pedals at the moment (e.g. Look, SPD-SL, Time, Speedplay, [...]).