Taking the initiative in doing the right thing. For example, when I worked at Data I/O, their LogicPak communicated via a serial line. This required a terminal emulator on the IBM PC side, and there were various ones of erratic quality available for the customers.
I just decided to write a simple VT-100 terminal emulator for the PC in assembler as a rogue project. It worked out so well Data I/O included it with every LogicPak for many years, as then the customer had everything they needed in the box, and Data I/O didn't have to support emulators they had no control over.
When something needs doing, I just get it done. If you wait for everyone to agree that it needs planning to be done at some point in the future, it'll never get done because the feature firehose never relents.
This has cost me a few weekends, but a) it meant that I kept my sanity in the long run and b) despite said fixes reducing the company's dependency on me (ie. supposedly damaged the job security) taking the initiative has allowed me to demonstrate a different and entirely more significant kind of value.
I'm sure this works fine for you, but I would in general not recommend that people do work on their spare time. The reason to do that is, as you point out, that you get to take all the risk, and your company gets all the profit. That's not, generally, a healthy employment relationship and as an employer, I would be pissed if I found out someone did that.
Just carve out an hour every day from your salaried time to chip away at these projects. Nobody will ever know unless you tell them.
Eh. The effect could be the same. I average less than 8 hour work days. But once every 2 months or so I throw myself at a problem at work I personally fee strongly about. This might spill into a late-night or weekend. But I like the rush of it and I get a lot of appreciation at work and it has materially benefited my career. Once I even got an on the spot bonus issues from the CTO for fixing a perf problem.
I just decided to write a simple VT-100 terminal emulator for the PC in assembler as a rogue project. It worked out so well Data I/O included it with every LogicPak for many years, as then the customer had everything they needed in the box, and Data I/O didn't have to support emulators they had no control over.