Unless something has changed recently, any main unit, lt5, or a6 as a slave won't give you any pwm control on that slave so that should guide you a bit.
Is this an Aquasuite configurator limitation or aquaero hardware platform? If Aquasuite - situation still might turn to better.
Its a lot of effort to go to just to have RPM reporting.
Why? The RPM reporting triggers alarms and notifications, this is a very good mechanism to maintain hardware authonomy as better as possible.
And 4x poweradjust units will consume much space/wiring/money than single Aq5 LT.