When you mean legendary summons do you mean gold? Majority of the gold summons aren't that hard to get over time and they happen to be the same as purple but can chase 2x (excluding the gold summons that chase after a 10-hit combo). For example, Rhino does the same chase as bull but can happen be triggered 2x.

Yeah I meant the orange summons lol, I've gotten used to calling the rarest things legendary xD

the orange summons are considered f2p yea, and they're not hard to get or replace.

although if you're considering making something "fully f2p" i'd avoid the orange 10 combo summons (like koh, guy's tortoise) and kirin, since these are super rares or require coupons/ingots to be bought. (ofc some f2ps do have koh/kirin but i think your target audience might be the kind who wouldnt spend on summons?)