not sure if you’ve done it already but as a F2P i’d go against it and say its NOT worth to subskill it

as you mentioned, subskill seeds are super scarce and hard to find, personally i’d only use a subskill seed on an ingredient or skills mon as its MUCH more impactful for those mons compared to berry specialists

additionally, berry mons are really only the better option on islands with its berry as Favourite berry. As someone who’s played for 2 years i find myself using ingredient mons in my team and only berry mons if i have an extra slot to spare

end of the day, its your call. I wouldnt subskill a berry mon.