The best client wrt TTN Community network is one that doesnt need them!
Downlinks are not community friendly and are best avoided where possible - hence the TTN FUP - you are aware of that, right? Clearly not outright banned as they are needed and a neccessary evil for LoRaWAN operation
Quantity and geographic distribution dependent this could be a problem if in a localised area as may represent a DDoS attack on the community.
Much as FUOTA it has a place and is perhaps best reserved for private network use and, even then not one peering with TTN as DL’s may still bleed over to the Community, taking capacity out of the available GW’s.
Bottom line DL’s render the sending GW deaf to ALL users uplinks for the duration, therefore we limit to max 10/day under FUP - and that includes LNS MAC commands, ADR instructions, Join process messages etc. and we steer users to think more like once per week or even per month to minimise Community impact.