How much knowledge/experience can be transferred between different categories/classes of certification?
The answers to your question lie in 14 CFR 61.159 for airplanes.  Your quoted times for the ATP in the airplane category are correct but some of that time is total time as a pilot, some is just in category and only a small fraction of it is in category and class.

For example, in your hypothetical situation, you have an ATP in ASEL category/class and wanted to add the get the ATP AMEL.  All you need to do (aside from any knowledge tests you may require) is 50 hours in AMEL.  Of the 1500 hrs TT in airplanes, only 50 are required in class.  This is the same to add ASES and AMES ATPs.  You could have a certificate with ASEL,ASES,AMEL and AMES all that ATP level all with only 1500 TT as long as you had at least 50 hours in each class.

The situation for rotorcraft/helicopter is similar and can be found in 14 CFR 61.161.  To get an ATP helicopter, you need 1200 hrs TT but the only hours that need to be in category and class are:


15 hours at night,
200 hours w/75 PIC, and
25 hrs in actual or simulated IMC


You could accomplish all of that within the 200 required hours.  The 200 hours needed in helicopter still count as total time and can be applied toward a fixed wing ATP. 

ATP powered-lift requires 250 hours PIC in category with some sub-requirements out of that 250 hours


100 XC powered-lift
25 night powered-lift
75 instrument hours powered-lift


The FAA does not currently issue ATP in rotocraft/gyroplane so you are out of luck there.



If you wanted to min/max optimize the above requirements and get ATP in all of the above the hard category and class requirements boil down to:


50 hrs airplane single-engine land
50 hrs airplane single-engine sea
50 hrs airplane multi-engine land
50 hrs airplane multi-engine sea
200 hrs rotorcraft helicopter


15 hrs at night
75 hrs pilot in command
25 hrs actual or simulated IMC

250 hrs powered lift pilot in command


100 hrs cross country
25 hrs night
75 hrs actual or simulated IMC



At this point you would have:


650 hours TT
325 hours PIC 
40 hours night
100 hours cross country
100 hours instrument


Now lets fly 400 hours XC in a single engine (slow and economical) with at least 60 of those hours at night and all of it PIC.

Now we have


1050 TT
725 PIC 


400 hrs airplane (at least)
75 rotorcraft helicopter
250 powered-lift

500 XC


400 hrs in airplane
100 hrs in powered lift

100 night


60 hrs in airplane
15 in helicopter
25 in powered-lift



Unless I'm missing something, this is all of the requirements for the ATPs except total time.  Go fly anything for another 150 hours and then take the ATP helicopter checkride.  Then fly another 300 hours in anything and take all of the other ATP checkrides with 1500 TT.



It is also worth pointing out that type ratings and ATPs are different things.  A type rating can be added to a private pilot certificate (though the checkride will be conducted at ATP standards).  You can also earn your ATP in an airplane that doesn't require a type rating (e.g. getting an ATP AMEL in a Piper Seminole).