I love Baines, Most Blues do but if we are offered 18 million I would take it. I know under Moyes we were horribly reliant on the Bainaar partnership, Most of our attacking started & finished on the left, Maybe we now have a manager able to make our playing style slightly less predictable. 18 million is a fair whack for us, I'm up for trusting Martinez with some funds to build his own team. Just my opinion.
We'd started to balancing things out but yes, we did obviously rely on that side heavily.
Most of our play, even on the right was based around getting it wide and getting crosses in - Baines was/is vital to that.
Might our attacks be more central now? Maybe. If so, as you say, that may lessen out reliance on that outlet.
Obviously it'd still be better having Baines there (look at the way Barça use their full backs) but he won't be there one day whatever happens.
A big(ger) fee would certainly help any transition, obviously.