Advantages/Disadvantages to a Dynasty League?

I've found a major flaw in our league. 12 team league, we play keepers. How it works is, in the offseason you each get to keep up to 2 players. When you keep a player you get them in the round they were drafted in, as your pick for that round. You may keep a player for 2 years, then they re-enter the draft.

But, we allow the trading of draft picks. Which hasn't been an issue until now but losing teams are starting to see the value of unloading players. If you drafted a good player early in the draft, but got a nice sleeper to keep for next year,there is no point in stashing that player if you aren't making playoffs.

The issue arises as I have attempted to trade McCoy/ Mike Wallace for a 2nd round pick + 6th.

And also, Jimmy Graham/Jamaal Charles for a 1st + 4th.

Owners are upset, and rightfully so. Essentially, I'm stacking my next year's team, and they're stacking current year team. And I lose nothing next year, they lose nothing this year. I see it as a flaw. My suggestion is to transition to a dynasty league, and just do a complete redraft and move on as a complete dynasty league going forward.

We have a stable league of owners so we wouldn't worry about people dropping out.

Thoughts?