Oh i think its always best when they allow for altcoin investments and not just the big 2-3. Even if they have to use a third party convertor that accepts altcoins and they get btc/eth, being able to invest third party coins that we have in a project is a great incentive for buyers.
It would be awesome for the project to consider various altcoin and not necessarily only btc, eth and xrp as a source of investment. The likes of dogecoin, xlm and Neo could also be considered to make the process swift and investors comfortable.