Dear
Without pressure pump, grohe sensor based fitting will not work as it operates minimum on 1 bar sensing pressure,without sensor it will give u flow but it will be depressing when u will not get desired flow as per ur expectation.
Yes small motors available you can deploy on individual washroom inlet with bypass option. In this case motor can install inside ceiling or at roof if supply line is dedicated.
If not grohe you can go with PORTA lever based fittings on 1st floors. It will run normal without pressure pump subject to you have used 40mm n 32mm pipe from tank till b4 fitting. B4 fitting almost 1 ft b4 32mm pipe gets changed to 25mm as fittings r designed as per 25mm size.
Lolz w.r.t last paragraph. Its not possible as when pipe will come up forward head will be balanced by -ve head so its not the case n grohe will not work on it.
Thanks