My league is similar to that. Are keeper list was due March 15th(yesterday) prior to the day keepers are due we can trade whoever we want for draft picks. After keepers are due trades are not allowed until after the draft, and we can still keep the maximum amount of keepers the league allows. The owner giving up a draft pick should only be allowed to keep as many keepers as your league allows players kept. Provided your league allows for tradeing draft picks I see no problem with any of it.
"Son we would like to keep you around here but were trying to win a pennant this year."