Possible phone charger

No, because the phone plus battery impedance is bigger than 2.5Ω, if you change that load the current will change too, so it won't work. You have to make that 5V almost the same for every voltage and load you apply.

It would only work if your phone draws constantly exactly 2A. Unfortunately this maybe only the peak load while transmitting to the network. While in so called Idlemode (while listening to the network for e.g. incomming calls) a good mobile phone (rf modem part) just draws ~1mA! This 1mA is also just an average value and is mixed outof cpu active phases while e.g. 80mA spikes are following longer periods of several tens of 4.6ms (for GSM for LTE its 10ms) of deep sleep while the current is even going down to a few tens of uA! All in all a mobile phone does draw current in a very dynamic range of 10uA to 2A!!! In case of 2A your circuit works fine, but for all lower currents your mobile will get a much to high voltage and will 100% be killed!

But if it's tied to the USB port on the phone (that has a built in charge controller) it should work, but as the battery reaches 100% I do expect resistance to go up and bad things to happen lol

Because I notice a huge difference between my 3A charger and my 1A charger, takes a third the time to charge :)