Pre-sign transactions with unconfirmed outputs

I’m wondering if the following scenario is possible: Any help would be greatly appreciated.

Alice and Bob are creating a (taproot) 2-of-2 multisignature together. They don’t trust each other. They want to fund 1 BTC each to the multisig address, but before sending the Bitcoin to the multisig address, they enter into a transaction where each multisig uses 1 BTC back (a buyback transaction). We only proceed with multisig financing if both parties have a copy of this undisclosed transaction.

Is this possible? To pre-sign a redemption transaction, you need to know the TXID of the output you want to send as a multisignature. Is that correct? So they need to go into multi-signature and create separate funding transactions that share the TXID with each other (but don’t broadcast it yet). Then structure and sign the repayment transaction. It then broadcasts the funds transaction. Is this possible or am I making it too complicated?

Additionally, what happens if the fee environment changes during this process and one of the funding transactions is not confirmed? Then, using RBF in a funding transaction will change the TXID, making the pre-signed redemption transaction invalid, making the pre-signed redemption transaction useless. Is there any way to avoid this?

thank you!

Edit: Here’s an example of a situation that illustrates what I’m trying to achieve: Alice and Bob want to start a venture fund. They don’t know which startups to invest in yet. Of course, they will only invest in a startup if they both agree that it is a good investment. So they create a 2/2 multi-signature for this purpose. However, I think about what would happen if the other party disappeared before raising funds or if an agreement on where to invest was not reached. They can block other funds indefinitely. So they want the option to literally end multi-signature with a predefined address.