You will be wasting your money and tearing your hair out. Don't do it.
The "non-mainstream" aircraft are far less likely to have approved mods to fit the kit you want and you can't afford to be the first if you are on a limited budget.
Time taken to do the fit, doubtless in small chunks as you can afford them, will eat into your available flying time (heavily). Also the time needed to work out the bugs.........Tearing things apart several times will be more expensive than doing it all at once.
Do you have the skill and knowledge to work with your engineers fixing the snags as they arise?
It might work if you have the aircraft on the N reg and a really good relationship with your maintenance provider but the types you are talking about are rare and may not be easy to use (or register) on the N.
At the end of it all you will not have a toy that is worth the sum of the bills.
What you are asking is not cheap. The aircraft is not cheap (relatively) and the required maintenance/checks will also be more expensive. You also need to factor in the costs of your training and recurrency. 25K, in any currency, will not do it.