Yes the Maus was an epic tank. Yes it was used in combat briefly. Yes this maus thing has been suggested over NINE THOUSAND TIMES.
The Gewehr98 is however, a good suggestion, as many G98's where called into action back in 1943, used by some scouts, Second line units like Artillery and Logistics and yes, the Gewehr 98 was also more accurate then the Kar98K, several germans snipers switched their rifles if they could.