I'd ask to spell out the particular concerns. It doesn't make much sense to try to respond without the other person giving more details. Otherwise you're going

I'd ask to spell out the particular concerns. It doesn't make much sense to try to respond without the other person giving more details. Otherwise you're going to be in the role of making propositions and the other side will be shooting them down. Make them argue their case and poke little nagging holes into it.