For thirty quid, it may be worth having it and just cobbling up a solution for the rear butt plate which costs nothing, then using it until it dies or you get something better. But spending anything on attempting to improve it is really going to be pretty much a waste of money, since for the same 75 quid you’d spend on sticking a metal gearbox in the thing and getting a new buttplate, plus the thirty quid you spent on acquiring the thing, you could have something which is okay in the first place, such as a Galaxy G5 MP5K or a G&G M4 or some such.
Even if you did tart it up, it’s still the equivalent of a cheap car with a fancy spoiler pop riveted onto the boot. It is what it is unfortunately, a decent airsoft gun is basically going to cost 100 quid upwards.