Changing the handgrip from OEM unit to one less canted towards the rear might allow better access to any selector, as well as possibly stowage within the grip for useful items.  I was never a big fan of the "Extended" selector lever, as the (outward) extension makes it possible for the lever to be unintentionally moved through contact with field gear and such.  Sometimes, a reasonably low profile is better, but YMMV.

FWIW, I constructed my own Ambi selector using two StG58A selectors, and with the inclusion of the SAW grip, both levers are easily accessible to my Med/Large hands.  Posted about this long ago here, and on FALFiles. IIRC, there was no Ambi selector available at the time.  IIRC, on my version, it was necessary to slightly modify the right side of the SAW grip in order to allow full movement of the right-side selector lever.  Trivial modification.

I did the same for an Ambi mag release.  In that instance, I used a Brit mag release/mag release screw, and silver-soldered a serrated pad onto the right side of the exposed lever mechanism.  Simple, and it works.  Again, nothing was available at the time, and details were posted here, and on FALFiles long ago.

In both instances, the current offerings from DSA are much less costly than the custom units I had made, long ago, and I suggest considering them.

Looking at current offerings of DSA Ambi Selector lever, and Ambi mag latch, I am struck by how similar they are to the home-made designs whose detailed descriptions I posted on the web, prior to DSA's offering such items. For the record, I am NOT saying they copied my ideas.

One thing I'd like to add.  I bought a DSA StG58A with OEM trigger group parts in superb condition.  I was never happy with the trigger, for various reasons, so I bought the appropriate kit for my particular FAL from these people: https://www.falconarms.com/spring-kits/fn-fal.html, and the change in the trigger feel was simply amazing.  Possibly the best single upgrade to my FAL.  Lightened the trigger to a reasonable level, but not too light.  I did do a little light "smoothing-out" of side surfaces on the trigger group components that seemed to be rubbing on the trigger housing, and I did change to an aluminum lower, which also is a very good upgrade, IMHO.  Disclaimer: no financial interest.

When constructing my Ambi selector, my primary concern, given the lack of any alternatives, and using a SAW-style grip, was simplicity of construction, cost of components, and usefulness under all conditions, especially including hands wearing winter gloves.

Using a back-to-back StG58A-type selector worked out all right, at that point in time.  As mentioned, I had to relieve a little bit of the top, right-hand side of the SAW grip to allow the selector full movement.

I say nothing about current offering from DSA, except that it looks a lot like my one-off.

I think that if I were to do it again, I'd modify the thing, and have the off-side (right-side) selector lever a tinch elevated (upward) in position.  As is commonly done with AR ambi selector levers, nowadays.

I experimented with "Extended" selector levers, and found them initially attractive, but too large when employed back-to-back in an Ambidextrous selector lever set-up.  Sometimes moved with/by field gear, and interfering with gloved use, when used in Ambi configuration.   YMMV.  The standard StG58A levers worked well under all circumstances, and were a lot cheaper than the  extended levers.  Posted about all this long ago on FALFiles.  YMMV.

If I can leave you all with a bit of hard-earned--and expensively obtained advice-- make sure your controls are NOT inadvertently moved (by whatever means), and that your winter gloves will not be a problem.

Not all Control devices will meet the above criteria.