GFCI for older pool

[MRK]

My pool, built about 15 years ago, does not have GFCI protection.  I bought a Siemens 125 Main Lug Load Center to install (Sold as a Spa Panel), as my existing panel is an older Westinghouse panel, and finding the proper GFCI breaker for it was daunting, and when I finally found one, is was crazy expensive, too. 

The Westinghouse box has two 20a breakers in it.  One breaker is 110 volts.  It is used for the light, a mechanical timer which controls a Pentair power supply for the salt-based chlorinator, and a small Orbit sprinkler timer with a single zone on it.  The other breaker is 220 volts.  It carries a second mechanical timer (now set to be on at all times) which "controls" a VS pool pump (that pump has max amp of 16 and it is programmable on its own).  The timer previously controlled a 1.5 hp main pump and a 1 hp aux pump used for a Polaris.   Those have both been disconnected and removed.

So the new box is here, and my question is how best to proceed with its installation.  I can:

(a) Place the Siemens 50A GFCI panel in the circuit before the existing Westinghouse panel, or

(b) Place it after the Westinghouse panel, or

(c) Buy and install a new 20a 110v breaker (probably also GFCI) and install the Siemens panel in place of the Westinghouse panel (removing and discarding the Westinghouse panel).

My inclination is to go with "(c)" because doing that will avoid adding yet one more panel to a wall which already has too many.  There are two pool timer boxes, a main load center panel, a light transformer box, a sprinkler timer box, a junction box, and a chlorinator power supply box.  (And yes, regardless of which option I choose, I plan to remove the non-functional mechanical timer box that's ahead of the pool pump. But that still leaves 6 boxes already on the wall, and adding the Siemens box would take it to 7.)

So... is there any reason not to go with option "(c)", and if so, should the new breaker also be a GFCI type since it powers the pool light transformer - or would that be unnecessary since there is a DC transformer powering the light?

THANKS for the help!  

Oh - should have mentioned... I have installed plenty of service disconnect boxes working in A/C installation, and I've installed new breakers and replaced breakers in existing panel boxes.  And we've moved several times, so I've installed more than my share of replacement (and a few new) fans, outlets and switches.  All to say, I am reasonably comfortable with wiring in general.  But I don't know a great deal about pools, and have never replaced a breaker panel.  So while I DO know enough to go upstream and kill the breaker which feeds the pool panel, and I have a meter to confirm the circuit is dead before I go to work, I don't know enough to know I'm not giving something up by removing the old panel.  Again, thanks for any help!

Lastly - I posted here rather than in pools simply because what I bought is a "Spa" panel.   So I am fine if somebody tells me I need to move this to another forum. (Don't want to break any rules or irritate anybody!)