I will tell you a secret. Regional markets are not crap because Jita exists -rather Jita exists because regional markets were (and are) crap.
Jita was created by players after the reshaping of the gates network. Jita was elected because a) back then Caldari was the most popular faction so Caldari space had a larger population b) it was roughly in the middle of the new network c) it was close to several popular mission hubs and d) it had easy access to Amarr space where some lowsec ores could be found in highsec.
Thus a team of dedicated industrialists/traders decided to stock the market there, an effort which took a couple months before mission runners, people stocking mission runner hubs and other industrialists/traders began buying and selling in Jita too.
Closed borders destroy the economy, not boost it. With Amarr cut from Jita, Amarr will decline -not in a year, but in three months.