What to do with £250k RSUs?

Wife and I are both just HENRYs (combined income of £220k -£250k). We have a mortgage of £525k, pension savings of £160k and are saving about £90k a year into pension combined (annually). We have very little ISA savings (<20k combined). Wife has about £250k RSUs (180k vested). We don't really need the money from it and are thinking of it as a bet on the company stock multiplying over the next decade or so. There is of course a concentration risk in doing this.

Couple of questions

How would you think about the RSUs? Bet on the FAANG firm to continue dominating or de-risk this ?

Are we making a mistake by over saving into pension Vs very little in ISA?

Note: We've been in the UK 5 years and spent all our previous savings on the deposit.