-Supposedly you can put a satellite grade splitter and use one line instead of 2 for receivers like 322,522,etc (that need 2 inputs)
That isn't supported yet. You will have to wait for DishPro PLUS technology.
DishPro is simple stacking ... all the channels from one satellite at the same time on one cable. Legacy LNBs output either all the odd transponders OR all the even ones, depending on voltage. DishPro gives you ALL of a satellite's transponders at the same time.
DP Switches (including the one built into DP Dual and DP Quad LNBs) give you a choice of one satellite at a time - and all transponders from that satellite. Theoretically if you dropped in a splitter the two receivers would only work if they were looking for the same satellite ... regardless of transponder.
DP+ is a different kind of stacking. Instead of stacking one satellite by Odd and Even it stacks the signals requested by the two tuners.
The lower spectrum of DP+ is a lot like legacy. 950-1450 MHz feeding tuner one with the receiver telling the switch which satellite and polarity to place in that space. The upper spectrum of DP+ is for the second tuner - tuner two telling the switch to stack a possibly different satellite and polarity in the upper band.
Older receivers that have two DP or Legacy inputs will need a special converter at the back of the receiver that will split the DP+ coax from the switch or DP+ LNB into two Legacy feeds. New receivers with DP+ inputs can convert internally.
DP+ LNBs are cool in a new way. The dual has two outputs ... which can feed a 522 or 322 on each output (or DP/Legacy receivers). But the LNB also has an input for a second satellite feed. One will be able to wire a second dish (Dish300 or standalone 105/121 dish) to the input and the outputs will be able to switch (two tuners per cable) between three orbital locations and any transponder. Basically a DP+34 with two cable runs into the house, and one cable link to the second dish.