You could change the reflector but you'd need to ask someone that has it and has tried as to which will fit in it. The spot is caused by the depth of hte reflector, the spill around the spot is the light directly from the LED (without being reflected). You could give it a try without the reflector in at all.
Wow! yes they look cheap, there's a LIdl close to me, so I'll have a look
If you've never heard of "Hybrid" they are also called "ready to use" Sanyo = Eneloop and Uniross = Hybrio.
Whereas a regular NiMH might loose 50% sitting idle in 1 month, a Hybrid will loose only 95%. Downside is the top capacities are (rated) 2100mAh where as regular NiMH are up to around 2800 (some are rated 3000 but not seen any yet tested near that).
If you had a rear light that lasted months on batteries, then maybe they will suit you. But if your front light is lasting 2 days on a charge (or even a week) it shouldn't matter... you'd do better with the higher capacity.
The REAL capacity of these Lidl ones we don't know yet, it could be over rated by miles...