Some brainstorm suggestions for possibilities to defuse the runspeed issue without a cap:

1.) Implement a certain accelaration time before reaching top speed (like 500 msec or so, dunno what's good, need input here)

2.) Make aiming more difficult at top speed by making the reticle close slower

3.) Make top speed use up a lot more stamina so that mostly short sprints are being used (like it was in BF2)

Regards