Best Brokers For PAMM

We are soon going to take quite a lot of people (a few 100 to start) into PAMM/Copy trading.

I was wondering if anyone could give advice on brokers that are reliable for this on small accounts?

We are already pretty good for $10k+, we have a very good deal for that and accounts of 1-2k+ we are OK for.

We would like to be able to benefit more people though by making the entry barrier as low as we can.

There are obvious logistical issues with it being so many people, the broker needs deep liquidity for one.

Also, if you could please mention is US clients are accepted/not accepted that would be helpful.

Thanks in advance for any suggestions you may have.