The following is a compilation of arguments in favour of the infrastructure funding plan proposed by Bitcoin ABC.
I'm convinced that all known and relevant actors of our current community act in good faith to promote Bitcoin Cash as a peer-to-peer electronic cash system for the world. For the reading time of this article I invite you to assume the same. I've previously listed the strongest arguments against the #IFP. Here's what I conceive as strongest arguments in favour of it, compiled mainly from Amaury's talks referenced at the end.
Business Developer Shouldn't Worry About Infrastructure Development
Independence in Maintenance of the Codebase is Essential
It's generally underestimated how much resources it takes to run a professional software-development team. The node implementation of Bitcoin Cash which has so far almost exclusively been used for mining (i.e. keeping the network alive) relied on backporting the Bitcoin Core codebase for maintenance. The latter has a multimillion-dollar development team leading the way. We need to afford the manpower to cope with this maintenance work ourselves. If we cannot and we continue to rely on backporting we won't be more valuable as the competitor: If Bitcoin Core were to disappear, we fail along. Hence, independence in maintenance of the codebase is essential.
A well-defined Roadmap is Essential
A multi-node ecosystem is ineffective in achieving consensus. Even the acceptance of a roadmap has previously been seen as collusive in the Bitcoin Cash ecosystem. Decentralization can eventually lead to atomization of the efforts.
In order to effectively develop toward the vision of peer-to-peer electronic cash system for the world a roadmap is essential and must be committed to. Cooperation among developers is fostered better in a lead-node ecosystem.
Infrastructure Development must be Incentivized Properly
Bitcoin Core is a perfect showcase to illustrate why infrastructure development must instead be funded on a protocol level. If it isn't corporations are incentivized to manipulate the Bitcoin development such that they can profit. Here, Blockstream succeeded in doing so, limited the on-chain transaction capacity, and profits from selling off-chain transaction solutions. In order to remove this incentive to manipulate infrastructure development, sufficient funding must be steadily ensured to provide a competitive payroll for well-trained developers with the required skillset.
The main cryptocurrency competitors of Bitcoin Cash by market capitalization are Bitcoin Core and Ethereum. Both have funds at their disposal which are at least two order of magnitude larger than those available to Bitcoin Cash. As a result they will continue to outperform our efforts even if they are 99% less efficient in their development. The coinbase is a natural fit to allow a steadily ensured comparable amount of funding in infrastructure development in order to compete.
8% of the Coinbase Totals Only 1% of the Total Supply
Only 2.5M coins remain to be initially distributed. 8% of those are about 200.000 BCH. That's less than 1% of the total supply and a reasonable amount to be spent on infrastructure development into the future.
This 1% is commonly understood as an upper bound because network upgrades are still scheduled every 6 months. This would allow development teams which provide higher-quality development at the same price or equal-quality development at lower price to out-compete Bitcoin ABC.
Business Developer shouldn't worry about Infrastructure Development
Any resources business builders have to spend on infrastructure concerns (node stability under spam attack with 100x load being the prominent example) are resources not spent on their business, diminishing their likelyhood of success. Successful businesses are ultimately the ones achieving adoption for the currency. To maximize the value of the whole ecosystem it is hence best if businesses need not worry about infrastructure.
Value-adding Actors should be in Charge
The almost unlimited access to information challenges human's power of comprehension. Conventionally more access to information is considered a higher good. Currently the information is so abundant that it becomes challenging to filter and digest what's relevant. In the context of Bitcoin Cash it means filtering relevant actors which add value to the ecosystem from social-media noise (see also General Network Council).
2020-09-16: add @Fidel note on 1% being considered an upper bound.
 Amaury Séchet, Back to the Basics, https://www.youtube.com/watch?v=By0w43NQdiY
 Amaury Séchet, Building Bitcoin Cash Culture, https://www.youtube.com/watch?v=uOv0nmOe1_o [transcript]
 Amaury Séchet, Bitcoin Cash Split and IFP and How to Solve Development Funding, https://lbry.tv/@DigitalCashNetwork:c/AmauryIFP:3 [transcript]
Very good summary of pro-arguments.
One thing to keep in mind is that the IFP would be subject to change or removal in the following upgrades, which are still going to be scheduled every 6 months. So the 1% of the total supply mentioned in the article is an upper bound, it could end up being lower.