Well, a lot of this conversation is highly subjective.
Difficulty - no, there's nothing difficult about finding the components via the activity itself (scavenging on a planet surface // mining // etc) as you simply have to beat the RNG which means
time invested. You either get lucky and find what you want quickly or spend hours upon hours until the RNG gods finally smile. These are annoyingly 1 ton of X which you can't buy and have to find. (aimed at Ziggy - saw his post during preview) and you have to store them in your cargo hold and not the batman utility belt (aimed at Jabokai)
That leads onto the thread title of "reward" which is highly subjective. If you have all the materials you need bar the commodity and you do spend hours, unfortunately, looking for that 1 recipe item you better hope the reward at the end is worth it. Given that the NPCs in due course will come with upgrades then you yourself better have them too (the more competent pilots and/or wealthy ones may not but the rest will) That leads you to the process of engineers itself which, bizarrely, took a layered-RNG approach which as you all know tends to favour the house rather than the player (even with the fudge by FD it's still too many RNG layers to be "rewarding")
So no, IMO, engineers isn't something you "do on the side" as the game doesn't lend itself to that.
Your opinion may differ of course