4 ohm or 2 ohm

Not a good idea.  You know that.  You can't get the same power to each sub if you wire all voice coils.  Mismatching speakers like that is called ghetto and I'll have to assume  you will want to max out available power as well, so that leaves out the option of using only one voice coil on one of the subs because you will have to limit the power.  So, is it possible?  Sure, it is, for what it's worth...

Wire the DVC 4 in parallel so it is a 2 ohm sub.  Use one coil on the DVC 2 so that it is a 2 ohm sub.  Series the subs for a total 4 ohm load on the amp.  Give the subs no more than 75% rated continuous power.  This way, each sub gets the same power.

More ghetto is to wire the DVC 2 in series to 4 ohms, wire the DVC 4 in parallel to 2 ohms.  Parallel the two subs to get a 1.34 ohm load.  One sub gets twice the power as the other sub. 

Bottom line is:  match your subs, so that you use all the voice coils and they all get the same power, and select a combination that will put an impedance load onto your amplifier so that it outputs at the level you wish.

But wait!

Are the 2 subs in the same enclosure? And I don't just mean speaker box, I mean do they share the same air space?

If they are in seperate chambers then why not allow them to see different wattage?

If they are in a single chamber box, each getting diff amounts of power, they will literally work against each other, cancelling each other out. They would have to get the Very same signal strenth, quality, and timing.

Your only option is to try to trade one for the same kind of the other, or just use one to begin with.

Because the idea of using multiple subs is to see a gain or increase in at least one of these areas:  efficiency, linearity, or SPL.  haemphyst's thread shows the utilization of dual subs to increase linearity for the purpose of SQ.  For increased efficiency, each sub must be provided with exactly the same signal to take advantage of the double cone area.  And this increase in efficiency can provide more SPL, if that is one's goal.

The speakers, combined together with wires, will provide a load on the amplifier that will cause it to produce current.  Providing a safe impedance for the amp to work with is only one thing to deal with here.  One must also justify the use of the second sub in the first place.  If it isn't outputting at the same level as the first sub is, it is not matched.  If it is not matched, one will see no benefit by using it and, besides, could actually get worse results than by using just the one well-executed sub installation.