Do you have a window nearby? I'm great with finding this kind of solution.
Is the property yours or a rental property? It's easy to drill the wall and add a second vent, if needed.
If the dryer is gas, you MUST have them vented outside and, just in case, add a CO detector to your laundry room for added safety.
Well, that's according to the codes.
HOWEVER.... If the laundry room is super well ventilated (for example my laundry room back in Brazil that was in a balcony with two walls completely open and always windy, high floor), then of course i didn't care about the vent
In my laundry room one of my gas dryers won't be vented... But I have two windows and a door constantly open, plus a fan, plus a CO detector.
Regarding the water lines.
In my laundry room I have only one laundry hookup on the wall... many washers have only one inlet (so you select the temperature on the tap, as they're portable). Other washers have the annoying ATC and some washers have both hot and cold fill and (thank God) no ATC.
I don't need to say my laundry room is a world of Y connectors and 4-connector manifolds and Y hoses. Right on the hookup, the very first connection is a Y-hose, so I control the temperature for all washers ONLY opening and closing the hot and cold valves. For washers that have "warm", i keep the selector always on warm so the washer fills faster, using both valves for whatever temperature I selected on the tap.
In my case it's even worse, because i have some washers with imperial threads on the valve, others with metric... Sometimes I change the layout and I have to stop and think.
For draining, it's even worse... i have a world of goose necks and drain hoses hanging on both sides of the laundry sink.
When I do laundry I usually use 5 washers, sometimes up to 8 at once. I never had to use more than that. Over the time, i learned how to sort everything first load all the washers, and then I mentally count seconds or minutes to start each washer in a certain sequence, so they don't drain all at the same time, otherwise it would be a disaster with the laundry sink overflowing as it's too much water for only one drain and a tiny sink. To make things worse, my apartment is 100 years old and the pipes are super old. (My apartment is so old that I have a coal gas heater, an octopuss heater and a Kenmore incinerator abandoned in the basement under the front house) Also, I synchronize the water temperature need, because if I run 5 washers I can quickly use all the hot water from my heater, so I start with the super hot and for the delicate items loads I already have warm or lukewarm water only with the hot tap open.
I always rinse in cold, so my heater has time enough to recover. Again, that's MY scenario, with several washers.... In your scenario, with only two washers, you'll have nothing to worry about and you will probably never run out of hot water, unless your heater is really small and takes forever to recover and you'll never have draining issues even if both washers drain exactly at the same time.
Draining is super easy as you have only two washers... squeezing a little bit (just a little because you don't want to strangle the drain hoses) you can usually fit two hoses in one stand pipe.
As you have only two washers (and I hope the stacked washer is not a super modern model that has the stupid ATC) two simple manifolds will do the trick.
One thing all washing machine collectors quickly learn: We ALWAYS manage to find room for one more washer.
