Need to upgrade (replace) a bolt-on-lug sub-panel

[Hamberg]

Short version...

Need to update a bolt-on-lug sub-panel and would like to know if there is any reason (code wise? NEC 2014 in our area) not to replace it with a breaker sub panel?

Currently the sub panel is directly adjacent to the main (see pics) and I can see why they didn't use a breaker panel, but in my (feeble) mind a breaker panel would add an extra level of safety (in that it would allow that whole "zone" to be shut down, from that panel - which I know is the exact same as flipping the sub breaker in the main panel)

 

[Sparky617]

Both of my sub panels are controlled by 100 amp breakers in the main panel under the meter. When my house was built in 1998 the main panel under the meter (one cabinet) the code didn't require a main breaker for the service. My main panel has breakers for the AC outdoor units, the range, a 50 amp EV circuit I just added and the two sub panels.

 

[Hamberg]

OP, add on...

sub-panel pictured was added 10 years ago when we had an addition built. That panel is full with one tandem breaker, (what I noticed today) the main panel has 3 double taps (??) and I need to add a sub-panel in the garage for light/outlet circuits and a 60amp heater, plus we are adding a shed that'll need a sub-panel as well (30 amp).

My thought was to replace the pictured sub with a 125 amp, 30+ circuit panel, move as many single breaker circuits as I can from the original main and run the sub-panels and 240v circuits from the main.

How's my logic?