alpine mrd-1005 for type r?

Yes, you can, and that's a way to take advantage of the dual voice coil configuration of that subwoofer.  The amp will power a load at 2 ohms and at any load higher (even though the manual says 2 or 4 ohms).  Look at the specified output into a 4 ohm load:  700 watts X 1.  Ohm's Law tells you that if you increase the impedance of the load by double, the power will be decreased by half.  Into an 8 ohm load, the power output would be 350 watts X 1.

You can series-wire your DVC sub to an 8 ohm impedance and connect it to the MRD-M1005 for a power output of 350 watts.  When you later add another of the same sub to the system (if this is what you meant by "decide to add on later"), you would wire the second sub the same as the first and then combine them in parallel to make a 4 ohm load on the amp.  The power output, then, to each sub would be 350 watts.

See https://www.the12volt.com/caraudio/woofer_configurations.asp

Why would you purposely mismatch the amp's power curve to the deck's volume, and then run a lower impedance load on the amp (which causes the amp to produce an inferior product than it would produce at a higher impedance load)...when you could instead legitimately control the power output by making the impedance load higher?

An amplifier makes the same amount of power regardless of how it's matched to the deck output.  The gain is the matching tool.  Properly set, it matches the output of the amp to the size of the input signal from the deck, resulting in the highest possible signal-to-noise ratio.  The wrong gain setting in either direction will cause an inferior musical product.  Set too low (at an expected higher input voltage), the noise in the signal is higher than it should be.  Also there is the very real byproduct of the user having the tendency to turn the deck volume up past it's own clipping point, which, along with the higher noise, sends a clipped signal through the amplifier to the speakers.  Gain set too high, the amplifier usually clips the signal all by itself. 

If you absolutely HAVE to get 500 watts out of that amp now, and 1000 watts later, you will need to use a change of subwoofers to achieve that goal.  Use the amplifier's output ratings @ impedance loads to figure out what subwoofer, or combination of subs, you will need to use.  That is to say, adjust the impedance load, not the gain, to achieve your goal.