We use both CR and a charterstone at Buyan market.
CR for people with a village (with decent security), charterstone for people without a village / hermits.
A charterstone is a decent ways to get people fast-travel access to your market. Only Lawspeakers and chiefs would have some trouble, since they would have to drop their LS/Chief position, to be able to leave their village, and be accepted into the market's village, for charterstone adoption.
It has it's security risks though.
Since you have to swear people into your village, to have them adopt the charterstone, the is the risk of them porting away / logging out, and becoming an undesired phantom village member.
We solved that at Buyan market by adopting the following procedure:
1) character who wants access travels to our market, by boat/wagon/foot.
2) He/she meets our welcoming party, and aggros one of them. This way, he cannot teleport / log out.
3) He/she is sworn in, and adopts the charterstone
4) He/she is exiled from village again
5) We drop aggro
This procedure only leaves non-summonable assault scents, so it's quite safe for the trader.