It depends how you look at these things. As a FTB you should still try it although as Red Onion said might be slightly harder with Estate Agents etc but i'd say it is possible. When you apply and draw down a mortgage with a bank they are giving you a loan of money. It is an agreements between the Bank and you. If you repay the loan in 2 weeks or 2 months or 20 years , it doesn't really matter. You have done nothing wrong only repaid you loan very quickly.
The excuse if anyone asks is that as a FTB you applied to all the Banks for a mortgage because you were not sure who would actually offer you one. Get all the offers in and then start the switching. If for example you had a good solicitor on board he could draw down each mortgage every 2/3 days and pay off each mortgage as the next mortgage is drawn down.
e.g BOI mortgage on Monday.
PTSB mortgage on Wednesday which pays off BOI mortgage.
EBS mortgage on Monday which pays off PTSB mortgage.
KBC mortgage on Wednesday which pays off PTSB mortgage.
Ulster Bank on Monday which pays off KBC mortgage.
You will need a good Solicitor to keep an eye on things but it isn't rocket science at the same time.
You are now left with an Ulster Bank mortgage and all the other mortgages are paid off and closed. You have done nothing wrong or illegal here. Absolutely nothing wrong only taking advantage of the cashback offers. As someone said earlier it is up to the banks to check if they are happy to lend you the money. You don't have to tell them you are going to repay the mortgage in 3 days time . Please don't be afraid of this process, if you are in a position to get 1 mortgage offer then you should probably get 4 or 5 more offers. Get the paper work together and start applying and go for it. €9,000 per switch is massive money. I'll happily act as your broker and get everything done for a small fee
.