Hi sorry, didn't see tag earlier. You have about three different questions so I'll try and go into all of them!
Lie flat position/recline
The 30 minute time limit (which is just a recommendation anyway) is only for the first 4 weeks. And this is most likely cautious for full term babies, as the study which led to this recommendation was done using premature and low birth weight babies. Will you be driving to your parents' in that time? If so maybe it's best just to stop once on the way, take DC out for 5 mins, continue. The reason the incline can be a problem is that if the baby's chin is on their chest, it's hard for them to take in enough oxygen. That's not an immediate danger, but if they're in that position for long enough then it will start to reduce their oxygen saturation levels which is dangerous over time.
You are mainly looking to avoid the chin on chest position, but any foward curve of the baby's neck is non ideal. This is caused partly by the angle of the car seat, and partly because of the curved shape of infant seats, and/or inserts which push the head forwards.
There are some properly lie flat cots that you can legally use in the car but if approved to the older regulation, they don't need to be crash tested. This isn't always made clear. The newer regulation ones do, but in any case they tend to be really expensive and/or only compatible with specific brand prams, and you can only use them until your child starts to roll over. Some people love them but I think for most people the cost/benefit ratio just isn't there.
The Cybex Cloud can't lie flat in the car, only on the buggy/outside of the car, so won't help with the positioning for longer drives. Although I actually find the shape of the inserts tends to give quite good positioning anyway, as the body insert is boosted higher than the head one.
There are three which do lie flat(ter) in the car - Joie i-Level, Nuna Arra, and the new Maxi Cosi Marble. There's no specific research that says you can ignore the time limits, but obviously you can use your judgement and make a decision for yourself.
The other option rather than a lie flat seat is to look at seats which have inserts or are shaped in such a way that they keep the baby flatter - I find the Maxi Cosi Pebble is good for this and Avionaut Ultralite and Britax Babysafe 2 i-size.
One other thing to bear in mind (sorry!!) is the slope of the rear seats in your car - sometimes if they have a steep incline that can affect the fit and angle of any seat, so you might want to look at this before you go any further into looking at specific seats.
Time/lasting
If you want the car seat to last at least 15 months you need one with a height limit over 80cm, preferably over 85cm. Some are smaller and don't last the first year. However this isn't necessarily a problem as you can get loads of seats now which rear face for the next stage as well, so if you need to change seats before 15m you can get a rear facing one, or one that does both directions.
Swivel/base
The Cybex is the only base that swivels. There are a couple of seats by Recaro which are bigger rotating seats that have a smaller baby carrier insert into the top of them, but neither are lie flat. But what you describe - being able to click the seat easily on and off the base - you don't need a swivel for that, that would apply to absolutely any car seat base, and most infant car seats have bases available.
Hope that helps. Happy to go into more detail (😬) on anything.