I've been using the Pure Freedom trolley for years and it's pretty decent. The version I'm using at the moment is very heavy though which is perhaps the biggest drawback but I think lighter models have now become more standard. The stream of water it generates coming out of the brush perhaps isn't as strong when compared to those using a van mounted system but it does the job.
You could always put it on a much higher setting if you were finding that a problem as well (I usually stick to around an 8-11 so as not to use too much water but it goes a lot higher). Tyres and trolley build and such are all sturdy enough.
Sounds like you could be using the same one as me, if it’s the standard Mk2 model (not the Nano) with puncture proof tyres. I’ve been using one of these for 13 years as it’s perfect for my work. I did originally consider the XLine aluminium version which looks similar with the exception of a sliding handle which I really did not like the idea of. It also wouldn’t fit in my car as it needed to go in a closed boot. The PF trolley was the only one that would due to the folding handle. I also found the weight to be too much. Unacceptably so for me, so I modified it.
Quite simply, I replaced the pump with a backpack pump (a straight forward swap for the 3x heavier Sureflo). This pump will run all day on a 7, 10 or 12ah battery depending on how long a day you like to do. Each of these batteries is a lot lighter than the 26ah battery that is fitted as standard.
I don’t use a battery box as I don’t find it necessary. I’ve modified the base so I can strap the battery on with a small luggage strap which makes it dead easy to swap out should it go flat.
I’ve also replaced the solid tyres with pneumatic tyres. Also much lighter than their solid counterparts.
Overall this almost halves the weight of the trolley and is very noticeable in use.
One recommendation though if you do this. Carry a spare wheel in case of punctures. It will happen. I bought a pair of spare wheels and always keep one in the car.