I think it would be viable to have separate looper blocks that you could add in - 1 minute, 5 minute, whatever. That should be possible. It seems reasonable. As far as I can tell, the limit is somewhat arbitrary.
It would be a good suggestion. I think Digital_Igloo suggested somebody put it on Ideascale at one point, or something similar. It's probably up there. I'd be shocked if it wasn't on one of DI's lists somewhere.
But here's the thing...they made the decision for a reason, and they have a lot more info about the inner workings of the box. Making a suggestion that they increase the time, that's cool. It's not a bad idea. But suggesting they intentionally limited the time with the intent of pushing sales of their 20 year old looper pedal is just ridiculous.
It's also worth noting that the hardware in things like the Helix isn't quite what the average person is used to in terms of a computer. The average computer may have a crapton of RAM that cost about $20, but it also introduces too much latency in real-time audio processing to be viable as a high-end guitar pedal. (Not all computers, but the average computer.) There's a difference between the processors in your PC and the dedicated DSP chips in things like AX and Helix. These are dedicated processors that make sacrifices in other areas in order to excel at the more important ones, like I/O throughput. Point being, it's not an apples to apples comparison. It's all fruit, but...