PTS must remain liquid and AGS must remain illiquid in order to honor the original agreement with investors of AGS/PTS. Anything else would be unfair and would result in a further loss of faith in the Bitshares ecosystem. Cross-post from the other thread:
AGS received a much larger allocation of DACs per dollar invested precisely because they are "locked" into the Bitshares ecosystem. Making them liquid after the fact is unfair. It essentially gives AGS holders all of the benefits of PTS without any of the downside. Here is the "company" analogy we like to use so much:
The Bitshares Corporation gives investors a choice between buying one of two corporate bonds, A and B. Bond A is perpetual and bond B is convertible. For this reason, A has a much higher yield than B. After the bonds are issued, the company turns around and says "just kidding," A is now also a convertible bond, though it keeps the higher yield. Just something to think about.