That's interesting that you ask that question; we had to address a hypothetical question like that on an exam in dogmatics class.
Suffice it to say I argued that while the Orthodox Church technically does not comment on sacraments outside of her visible boundaries, she is the bestower of the sacraments and as such may act with economia (the bishop may relax the strictness of a canon).
Since we can ascertain ecclesiastical reality outside of the visible Church (as Florovsky once said, the charismatic boundary of hte Church is not equal to its canonical boundary), I think it is good to receive via economia. The sacrament is not considered "valid" before entering Orthodox; no, it is only made full by the act of joining oneself to the body of Christ.
I also argued that since the Church may decided at any time to act according to strictness, baptising a convert is a valid option, too. Basically, what it comes down to is: it's between the bishop and you. So tell anyone that complains that you "violated" your baptism that you followed the Church's will and you cannot be attacked for that.