Absolutely they could. All the entries so far can do even better with more RAM. That PAQ entries have command line flags to do this. That's already known in fact.

What this is looking for is fundamental improvements, not "i brute forced a known way to win this competition".

An element of compression is usually a search problem - 'lets try all these ways to encode the data, and see which is smallest'.

Therefore to maximize compression, you tweak parameters to search as hard as possible, and therefore use all the time.