Can this battery swap be done safely?? (help)

[REDLINEVUE]

I bought one of those Black and Decker Pocket Power packs and decided to take it apart... Inside, i found what appears to be EIGHT 1.2v Ni-MH batteries..... would it be possible for me to "upgrade" this unit by swapping these batteries with some 2650 Duracell's or maybe some eneloops? it usually takes about eight hours to charge the pack so I'm not too concerned about the charging rate but would love a bit more capacity.

Is this possible... please feel free to add any info, ideas or cautions you may feel appropriate for this "project".

Thanks