I am a GM here (i have GM'd for 2 years now, but this is my first PF2e campaign) and I'm worried about my party's balance.

We currently have a Tempest Oracle, a Redeemer, a Gunslinger, a Thief Rogue, and a Fighter. For some important context, i like running difficult combats (don't worry, I'm not throwing severe encounters at them every day or anything like that, but i do like my combats to be tense and for my players to have to properly prepare for them). The party was told this at session 0, and knew to expect a campaign where the combats were difficult.

My main problem is with the Oracle. While a great player (and I'm really not just saying this because i know all my players are on reddit, she is a great player) she feels discontent with her role as sole spellcaster and sole support, as that's not what she wanted. This was going to be a 5e campaign, but we switched before any session were played, but her character concept stayed the same throughout, which went from Warlock to Oracle. Anyone who knows 5e warlock can tell how different those two classes are.

I feel stuck, because i feel like im trapped between two things: Firstly, I do want everyone to be able to play the way they want to play and be happy in their role. Secondly, I want to make sure that this party is set up for success, and while this party can certainly output damage, I'm concerned by their lack of spellcasting and ability to deal with problems that a spell caster might deal with.

The player has expressed wanting to switch to Kineticist when it comes out, and i did state multiple times this is a new campaign in a new system, so i would let people change classes if they didn't end up liking them. However, this party would lose all their support and most of their healing. Even if they dont switch, they have been building and playing their Oracle blaster first. While i have said before that this is a difficult campaign and obviously in a difficult campaign death is on the line, I would much rather have a death come from a tactics issue than a team building issue.

Do I let people make the classes they want, and let the consequences come as they may? Am i overreacting to a non-issue? Should i let my players try to overcome their team deficits by smart tactics? I just dont want someone's work on a character to die for this.