I say officers are heavily linked with Remnants because the player needs officers to fight Ordos.
In essence, you can demote officers into mercs by switching to the +2 officer skill and then re-speccing out of it. It feels like an exploit, but that's basically the only way to guarantee you get mercs with the skills you want.
Useless to me since none of my games used Officer Management, and I will not respec multiple times to get mercs like this (thanks no bonus XP refund for respec). The only time I respecced like that was to swap s-mods on Ziggurat (by toggling BotB on and off) after I swapped from human weapons to Omega missile weapons, and that was a one-time deal (no need to respec a second time). I did not like swapping s-mods like this (two SP lost without refund from respec).
Chandi gives good advice - there are so few money sinks in this game but so many ways to earn money that it is silly to avoid mercenaries because of the money cost. The story point cost is slightly more valid - although you get a 100% exp bonus for hiring a mercenary from a comm log, you get 0 bonus exp for extending their contract. I think mercenaries are well worth the SP tax, and the money tax is almost completely irrelevant past the very early game.
That may be true late, but before that, I need all the money I can get to buy my ships, build up my colonies, and all the supplies and fuel I need to feed my fleet.
I need my SP for skills, s-mods, and sometimes colonies (improvements or new stable points), and a few in reserve to escape combat or select real story event options. I do not feel like I have so many SP until I start grinding endgame fleets like Ordos at +500% xp.
I like building up colonies, and I want a huge pile of SP on hand to splurge on multiple colony improvements thanks to 2^n costs. In practice, I may use few improvements because I need a big pile for s-mods first.
P.S. Currently, I have not made officer skills elite because of fire-and-replace.
P.P.S. The biggest money sink is Restore when I have hundreds of clunkers in storage. In one game, I had over 20 million credits in reserve, but it was not enough to Restore the hundreds of ships I collected and put into storage. I only feel like I have too much money when I can afford to restore every ship I want to collect to pristine, and I never got that much money.