You are describing late stage PTTD (Posterior Tibial Tendon Dysfunction). Do you have any issues running?
It is hard to control late PTTD with an in shoe cycling orthotic. An above ankle brace works great - but few want to wear one. Most cycling orthotics are utilized for forefoot hot spots (metatarsalgia generically, often confused with or even having things like lesser MPJ capsulitis or Morton’s neuroma) and generalized arch tiredness/aches. True structural support (that you may very well need), requires a very firm/rigid device. With your high arched foot, this is tough because of the low volume in a cycling shoe. A rigid carbon custom one would be best, but your “ankle” (more specifically your subtalar joint since your ankle mainly only has motion in 1 plane, dorsi/plantarflexion) will still collapse inward some. External cleat wedging will also not help much at all. Long term, an FDL transfer surgery could be indicated.
Best of luck!