Every year, IBM is at the user conference for the software we currently use. They're always showing off their newest Linux machine with 200 cores and I don't know why, because half the people there aren't even using bar coding, and everyone there is a small fry.
Here's where a niche developer comes in. You can use Java which is supported by IBM, Zend has a nice PHP setup, and IBM's bastardized version of Apache. Want to build an API to interact with this stone age fucker? You can do it. Build a Slack integration and look like a hero. Heck build some crappy web app because it's easier and faster to do development with your favorite framework than it is to do it on the IBM with RPG and whatever the fuck that thing runs. SQL your brains out!
These customers aren't leaving the IBM without investing a half a million dollars into a new platform. Every year, there are less and less people there, but they'll gladly spend $50k to integrate some simple workflow.
Rent a booth for $1,000, give away an iPad or some FitBits and pass out some business cards. Go to 3-4 of these a year and you should be able to keep busy for a while. And you already know SQL, PHP, Apache, you just get to discover the 'intricacies' of doing it on the IBM.