I have several monsters that I want to keep for the long haul (Red Choco, Cloudburst, Goblin Chief) that I got early on. I can't start assembling the top tier infusion monsters yet, but I don't want to go through the game keeping them as virgins.
Question - Is it safe to infuse abilities that you know will be replaced by a higher tier of the same category, as long as no junk passives are passed?
E.g. Pretty much every build ends up with HP30%, so will it be a problem if I started passing HP25% (Pulsework Knight) to everyone before then? I am slightly worried that if a passive with lower tier than HP25% will be needed, then this may cause a problem?
On the flip side, I have been avoiding passing junk passives, but I am beginning to wonder if this is even a problem. For example, I'd like to start passing Cloudburst some -a spells, but most monsters would also pass junky resist passives. Again, is this a problem later on?
What I am avoiding is being screwed late game because I have unwanted abilities I can't get rid of (or can't put desired abilities). This coming from someone who played lots of Persona 4.
I don't want to sound useless, but if it may be some help then take note. What I think you should do, is just go along with the flow, use monsters, level them up, ditch them when you find something better, and when your at your very peak in the game, then go back and try get the same 3 monsters you currently have, and just have a field day leveling them up to their highest tier, also, late on the game, you should have a lot of spare very good monster components, if you do not desire to do that, then sorry for wasting your time lol.
I do think it's possible for early infusion to create problems with the "build recipes" presented in the Monster FAQ, but I don't think it will create any problems that can't be solved with minor tweaks to the infusion process. It sounds like you have a decent understanding of the tier system, so you should be able to figure out workable infusions when you are ready to assemble your finalized passive ability lists.
That said, any monster ally* can have its passive ability set fixed no matter how messed up it gets. In a worst case scenario, you can use several yellow-locked low-tier abilities to "flush" the monster's entire passive ability set, and then (re)infuse your desired abilities. This technique is rarely necessary; most problems can be resolved with yellow locks on desired abilities.
*(Caution: if you don't intend to get the Perpetual Battlefield DLC, be very careful of Pack Mentality--and by extension, Chichu--if you intend to use that passive; its sources in the main game are very limited, and its low rank makes it impossible to retain if you make a mistake with it)