I have been considering this model for some time. I recently got into the 1/5 scale myself. At the moment I am running the lower cost options (clones): Exceed, Rovan and King Motor. Looking at the
Losi 5IVE-T or Vekta.5 LSE as my next vehicle. I was uncertain what to get when I opted into the 1/5 scale since my 1/10 nitro on-road cars have gone into retirement as there is no practical place to run them after moving to NC.
Places like DDM and Detroit Performance RC (in USA) are good places to look for upgrades when that time comes. Better quality parts and it is usually specified what raw materials the components are made. There are other places in the UK such as Taylor RC, Innovative RC, and others. Keep in mind things will break when you hit a wall or large object such as a tree, post, curb. The more mass you add to the vehicle, the more damage you get along with it on impact.
What others have stated, a remote kill switch is your friend as it will shut the engine off due to signal loss, low receiver voltage or erratic glitches. Best to have a 3 or 4 channel receiver so you can use that extra channel as a remote engine kill switch since some runaways occur due to other issues like something jammed into the throttle linkage that may prevent the servo from operating.
Another important mod from the start would be an outerwears cover for the underside of the motor, one for the pull start and one for the air filter. Best investment at reasonable cost. I just ordered a few sets to install on my current rigs as I am tired of having to remove the engine cowl in order to remove the compacted grass that tends to pack in around the magneto coil. Doubt it will catch fire but will cause the engine to overheat if you block off the air flow on the motor head. This will also prevent large objects from damaging the flywheel blades. Note: you may need to apply heat to the screws that secure the motor to the chassis as you will have to remove the motor to install the outerwears cover on the bottom of the motor. The fasteners should have been secured with thread lock so heat may be essential in order to break free the screw to prevent stripping out the hex socket. Perhaps this can be left for later on. Having a source of compressed air will help clean out grass clippings and other objects that get sucked into the flywheel cover.
Last thing, go through the proper break in process on the engine. It should be in the owner's manual how to do it. Pay attention to proper oil/fuel mixture.