Behavioral Finance ideas make a lot of sense than the EMH crap that i got dished out!! ;-))
" ... the more convinced I became that I should have no discretion whatsoever about when to buy and when to sell a stock".
My own take on this is that "discretion" is generally something best used when OUT of the market and DESIGNING a system, rather than when IN the market trading it.
"... interested in holding a portfolio of equities over a period of 6 or 12 months...."
I have done a lot of trading systems design (before and still currently outside of Q) and with regard to equities, for the most part i don't even try to design the timeframe, i just let the logical rules (partly fundamental, partly technical) tell me when to hold & when not to for each stock, and the holding periods can turn out to be anything from a few days days right up to more-or-less indefinite in some cases.
Staying invested the whole time, but changing the investments as the rules advise, that makes good sense to me too, although with the caveat that although we haven't seen a bear market for > 10 years doesn't mean one can't happen. What do you do then? Get out or try holding inverse equity ETFs?
Yes, Greenblatt's ideas are good too, but the more you look at fundamentals, the more you can find other ideas that work but no-one has really written about. That's mostly what i am playing with right now here on Q.
Regarding illiquid stocks (e.g. speculative mining, biotech, etc) they can sometimes be fantastic "investments", but just don't want to be holding them if/when the market as a whole goes down. Yes, i agree with the "my order size < 1%% of av daily volume" type of idea too.
Excluding stocks with old (i.e. no recent) data:
My analysis for my own trading is not here in Q and honestly i am not a good python programmer, but i will think about this and, if i can't figure it out, then i will try asking around a bit. Certainly the idea makes good sense and worth doing.
All the best, Tony.