I totaly agree with you mate the idea of giving the option to catch one of the 3 legendarie birds is fantastic (not a big fun of regis tho) but it would be amazing to get a zabdos.
Also a great plus would be if we could get Latios or Latias. :D
Ending as my favorite legendary Darkrai would be a dream come true xd.
So it would look like this...
KANTO:
Catchable (Mew & Moltres , Zapdos or Articuno)
Data only (Mewtwo)
JOHTO:
Catchable (Celebi & Raikou , Entei or Suicune)
Data only (Ho-oh , Lugia)
HOENN:
Catchable (Jirachi & Latios or Latias & Regirock , Regice or Registeel)
Data only (Deoxys , Groudon , Kyogre.Rayquaza)
SINNOH:
Catchable (Darkrai<3 & Manaphy & Azelf , Mesprit or Uxie)
Data only (Dialga , Palkia , Giratina)