im biased as i've gotten my miners and have already recouped half of 1's cost but I say let him keep them to use with a couple untouched as warranty devices.
that or maybe he allow arklan to mine with them keeping his original percentage fee and then doling out the rest as dividends appropriated to the groups purchase percentage of each individual in the buy? I have free power so I'd offer to host the pooled collective but judging from how up in arms everyone is I dont know if its worth it.
Final thought on it is arklan did a great job I got what I paid and he was upfront about getting extras, if people feel jaded by this arklans reasonable and im sure he'll make a good decision even though per the terms he shouldn't have too.