I'd hang on to your deffkoptas, rather than biking them.
In part because the defkoptas would make HUGE bikes (but great buggies) but mostly because deffkoptas are a great unit when used right (and now in plastic

I have several of the fugly old metal ones...gah! ). Deffkoptas can deliver a fast-zooming alphastrike that bikers just can't match
Regular bikers are a bit meh. Nob bikers aren't bad against some lists.
As to the rest:
You have the core of a decent footslogging or Battlewagon rush army there (need BW's for the latter).
Snikrot + commandos can be a nasty surprise for enemies
You could do trukkrush boyz mobz, but they aren't as good in small squads of 12 as they are in meaty 20+ man squads. Tis is countered somewhat by the express delivery pain that 6 trukks full of boyz with
PK nobz can deliver. It;s down to your preferred playstyle there. The
KFF mek riding along will add to the survivability
What you are lacking is fire support. Lootas do this well, as to Big Gunz (Kannon especially) and similar. You have a lot of anti-infantry punch so far, but could use some more anti-vehicle.
You could use the spare warbosses as Meganobz, with a little tinkering/proxying. They aren't bad if used right