Smaller is harder but I'm not sure it matters. One of those magnifying circular light dealies is recommended. Parts count is the killer. I just finished the prelim parts list and pushed it to github. There's 320 parts on that 10x10cm board. Ouch!
(Someone please send me a Pick n Place machine)
70% of those parts are decoupling caps for the ASICs. Is it really necessary to have 14 per ASIC? As a back-of-the-envelope calculation, I get about 5 nC of charge per clock cycle (based on 1.5 A @ 282 MHz). With 0.8 uF of lumped capacitance, neglecting ESR/ESL, that's about a 7 mV drop, which is small. Maybe you can get away with less? Maybe you can use larger capacitance values but fewer caps overall?
I suppose the only way to know is to do some in-circuit testing on actual ASICs.
At this point I'm assuming the Avalon guys know what works. Usually you can't put in one big cap instead of many small ones because of frequency response. Essentially a big cap won't filter high frequency noise but the small ones will, and the bit twiddling is high frequency noise (one bit interferes with another bit).