just in case its rains? is a heat shield for bmw 528i cold air intake safe to install than to install into fenderwell which is better and safer

The BMW comes stock with a CAI and it has been dyno-proven numerous times that no aftermarket CAI improves power or economy. In fact dyno tests have consistently proven the opposite; that all CAI's for the BMW have been detrimental to power output decreasing it by as much as 14 HP!
Realize that an intake system isn't just about a tube and cool air. The size, shape, and routing of the intake air all impact the power band and BMW has spent millions engineering it.
For instance if you were to restrict the intake runner at a particular point you can actually increase torque at a specific RPM. Moving that restriction will more the RPM range where maximum torque is realized.
Only one CAI was PROVEN to increase HP in a BMW and it was an $800 Carbon Fibre unit designed for the E46 M3.

But to answer your question. As long as the inner liner for the fender is in place moving your air intake into the fender is fine.

If you are using an oiled filter with your CAI get rid of it if you value your car and its engine. Again power is actually DECREASED when using an oiled filter and damage can occur from the 27 micron material getting in as well as the oil contaminating your hot wire in your MAF.

Edit:
In order to get some extra HP (engine will breath and rev faster) you can swap out your intake manifold with one from the M50TU engine. You will loose some down low grunt but that 3600/4000 RPM 'push' you get now will be even stronger.