Even if the arapaima has to be housed in the 150g temporarily, no, you can't mix it with a jardini. If your jardini is already attacking anyone, then your arapaima will likely suffer the same fate.
Just because the fish is going to be big doesn't mean the Jardini's behaviour is going to change. The Jardini is being territorial and needs more space or fewer tank mates.
As for the pima it's going to also need more space than a 150g or a 210g these both a enough for a lone Jardini. Think big...real big... plan and do your research.
Pima pond...Jardini 210g try lightly stocked.
Tank requirement was not your question and im sure you know what you got and what its needs will be in the time ahead. With that being said and to answer the actual question; I think it's clear that you can't keep your specific jardini with your other tank mates, including the arapaima. Generally you will find the majority of jardinis to behave in the manner you described (with exceptions of course). Many variables can change whether they will live together without quarrel or not. You may not want to risk experimenting though depending on how much you have wrapped up in the pima. Would be more informative but it's about 1:30am for me and im already looking at this half crosseyed, lol.... Maybe more later. Good luck.