Personally I disagree with it.
1. While it is true that it could create an EXP sink, I think a better alternative could be done. For example, let's say any Pokemon over a certain EXP mark like 1 million would require a Trade Tax. Maybe you pay a certain amount of money based off how much EXP the Pokemon(s) you're attempting to trade, obviously the more EXP, the more you pay to trade. Anything under the million would be no charge.
2. It would discourage a lot of players from training Pokemon, a lot of players like to train exp in order to get the much rarer Pokemon.
3. EXP helps climb the ranks in Vortex, it would make climbing that latter much harder.
4. If someone wants to start on a brand new account, but take a Pokemon that's special to them with a lot of EXP, they're left out.
Long story short I feel their are better options. Maybe a trade tax or a limit on how many times you can trade daily. I know this doesn't affect tainted Pokemon. Or you could possibly do a exp tax. Maybe like every time a Pokemon is traded, 5% of it's total EXP gets removed.