Hey, can I have one of the Cyndaquils? I'll give you a (legit, of course) Totodile in return so you can keep going! :D
Oh, and if we absolutely must take 5 Pokemon... I'll give you 4 more Totodles in exchange for Charmander, Elekid, Turtwig, Mudkip.
EDIT: If I misunderstood something, please tell me! I'm very confused about what you mean by Rule 4...