.1. I am not sure the lights would work at full brightness all the time, with a DC controller through a decoder you are still only putting a few volts through to make it move, the same (if not less) volts than would be required on D.C. without a decoder fitted.DCC fitted locos will often work better on DC than unfitted locos for a few reasons. These things will often be better:-
1. The lights work at proper brightness all the time.
2. You will get inertia built in to the loco (no need for an inertia controller).
3. Less likely to stall when running slowly.
4. No need to fit a decoder when you convert to DCC.
This is all conditional of course on the decoder that is fitted being any good, and that DC mode is enabled, and that you don't have a fancy PWM controller which can cause problems (a pure simple regulated DC controller is best). I would recommend that you buy the loco, and if you have trouble with it on DC get an inexpensive DCC controller (like a Bachmann E-Z Command for example) and see how it goes with that. An adequate DCC controller costs a lot less than a good DC controller.
Sorry, my quote on note .2. should have been .3. I couldn’t see how less stalling would be possible, quite correct.My observations on this:
1. This depends on the decoder, some do, some don't.
2. DCC decoders have voltage controls built in to tightly control the voltage supplied to a motor. These are based on the principal of dropping the voltage from a higher voltage. You can never get more voltage out than you put in. So while a DC controller drops the track voltage, the decoder will be trying to maintain the voltage to the motor, but won't be able to due to insufficient track voltage. You are likely to get a conflict here with undesirable/uncontrollable behaviour.
3. This is not true. The DC track voltage is dropping off, so the effect will be exactly the same as it is for normal DC operation with no decoder fitted: it is more likely to stall due to continuity issues between rail/wheel with low voltages
4. That is true because the loco will already have a decoder fitted.
My suggestion is: don't bother running DCC fitted locos on DC. They will never exhibit their full functionality to its potential, therefore, running on DC is always going to result in disappointment. Move to DCC and you won't look back!