日本にいけるといいんですが　the last が is though. By putting が　at the end , you can mean that you hope it will realize but it will not realize soon because of some reasons. 日本にいけるといいんです　This sentence is not formal Japanese. My husband and I never say this way.Young Japanese may say like this. Probably it means I want to go to Japan. This strange Japanese seems to be used in Manga,maybe. I recommend to memorize only first sentence.

It is quite difficult even for me, Japanese native speaker, to answer. Let me try. But I am not confident to be right, so please take this as an opinion than an answer. I think the point is "が", which means "but" as you probably know. (1) 他に良い手段があればいいのですが (2) 他に良い手段があればいいのです Both mean "I hope there is another way", however #1 implies "--but there is no other way". On the other hand, #2 simply means it without implying anything, it is neutral. I can say as follows: (1) I hope there is another way, (but I don't think there is) (2) I hope there is another way. This is my opinion, and I suggest you to look at other answers. 他にもっと良い回答があるといいですね。

The essential function of a conjunction 'が' is "結論の保留",'reservation of conclusion'. - 日本に行きたい 　->　「私は日本に行きたい」is the final statment. - 日本に行きたいのですが 　->　「私は日本に行きたい」is not final statment. some other information is yet to come. - 日本に行けるといいのですが… some other information is yet to come. that can be 1).「本当に行けるでしょうか？(can I really go ?)」 　2).「お金がありません( I have no money)」 　3).「あなたはどうですか？( do you want to?)」 1 and 2 are negative, while 3 is not. - 今日は会社が休みだが、映画でも行くか 　-> 「今日は会社が休み it is day off today」 is not final conclusion. Something must follow, and 「映画でも行くか(go to the movie」 is the conclusion. ---------------------------------------------------------- *** The following conclusion can be both positvie and negative to the precedente sentence. - 「和食が好きだが、刺身は嫌いだ」 　-> 「和食が好き（I like Japanese food) 」：a starter sentece. 「刺身は嫌い(I don't like sashimi)」 : the conclusion. - 「私は和食が好きだが、特に刺身は大好物だ」 　-> 「和食が好き（I like Japanese food) 」：a starter sentece 「刺身は大好物（Sashimi is my favorite)」: the conclusion. '-------------------------------------------------------------------- >Besides, I remember there is an anime called >"Sakamoto desu ga". What is the meaning of が in this case? Again, 「が」is just "reservation of conclusion". Conclusion can be positve or negative (or neutral, or everything). -「わたくし、ＸＸＸ社の田中という者ですが、今日は新製品のご案内をさせていただきたく伺いました」 ------> 「わたくし、ＸＸＸ社の田中という者です（I am Tanaka from ＸＸＸ comapny)」: a starter sentence 「今日は新製品のご案内を…(Let me introduce our new product)」 : the conclusion. - 「坂本ですが？http://www.tbs.co.jp/anime/sakamoto/」 　-> 「坂本です（I am Sakamoto) 」: a starter sentence The conclusion can be: - 「何か私にご用ですか（do you have something you want to ask me?)」 - 「それが何か？（so what?)」 - 「今後ともよろしくお願いします（It's pleasure to go on working　with you(?))」 Or you can even say: 「はじめまして、坂本という者ですが、あなたに一目惚れしました」 "Hello, my name is Sakamoto, and I've got a crush on you"