Questions on dynasty league trades

I’m trying to start a league with some friends but I’m struggling to find information about sites that would let us do what we’re aiming to do. Here’s what we’d like to be able to do:

Part way through the year, Team A trades Russell Wilson to Team B for a 3rd round pick. Team A now has an empty spot on it’s roster which it fills by making an add, and likewise Team B has to drop a player since it’s now over the roster limit. Come draft next season, Team A now has two 3rd round picks, but doesn’t get a pick in the last round, otherwise it would have too many players. Meanwhile, Team B does not get to pick in Round 3, and will finish the draft with one less player than everyone else (which it can just add off waivers later).

Does anyone know of a site that allows this? Any suggested sites? Thanks for the help.

MFL can do all of this and/or as commissioner it can be managed easily.

One note, I assume you would not want Team A’s last round pick to evaporate immediately. If they subsequently trade that 3rd pick away, they would then be down 2 picks. Is that expected?

In MFL roster is one thing, draft picks are another. You can’t draft a player when the roster limit is met.